Take a country in the modern day, like the U.S., which routinely makes use of weapons such as guns, artillery, drones, tanks, et cetera. Now imagine that everyone in one of its elite squads of soldiers suddenly gains the power to shapeshift into a T Rex. While in Dino-form they retain full intelligence and ability to understand human speech, as well as being able to transform back and forth at will (let’s say the process takes 1-2 seconds).

Would these new powers actually be useful in the setting of modern warfare, or a huge liability? I imagine that a T Rex would make a large target, and be less effective at killing someone than a simple gunshot. Or would the sheer intimidation factor make them a valuable asset?

Would it make a difference if instead of one squad, it was the entire army?

Edit - Answering some questions:

How big is a T. Rex? - 12 ft tall, 40 ft long, weighs possibly up to 14 tons.

Can T. Rex's swim? - My first guess would be no, but Micheal Chrichton's T. Rex could swim, just like a crocodile. I would guess he knew a lot more about it than me.

Where does the extra mass come from? - They transform the same way Bruce Banner becomes the Hulk (ie. pocket universe/hand-wave?).

What happens to their clothes? - Ripped off. If they try to transform while wrapped in steel chains or something, they would likely be seriously lacerated or strangled.

How much do they eat? - It is viable to get hungry as a T. Rex, transform back into a human, eat, and then transform back into a T. Rex. However, they need to stay in human form long enough to digest the food and gain energy from it.

What happens to injuries when they transform? - If an injured human shifts to a T. Rex and back, they will still be injured, though for a sake of drama let's say that injuries that would be dangerous on the human form aren't as dire to the T Rex form. This would force people to remain as T. Rex's or bleed out!

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    $\begingroup$ the shear "wt# just happened" (aka, "wt# did I just read") hesitation/confusion should be considered a pro in favour of their effectiveness. $\endgroup$ Oct 27, 2017 at 18:12
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    $\begingroup$ i.pinimg.com/originals/83/49/b6/… $\endgroup$
    – L.Dutch
    Oct 27, 2017 at 18:25
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    $\begingroup$ Somebody didn't think this plan out. I have a big head and tiny little arms..... $\endgroup$
    – Thucydides
    Oct 27, 2017 at 20:21
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    $\begingroup$ Shapeshifter starts out human mass but somehow becomes as massive as a T-Rex ? Where did this extra mass come from and where will it when the shapeshifter changes back ? If you're going to retain any relationship with our physical world, you can't simply create that much matter and destroy it at will. $\endgroup$ Oct 28, 2017 at 1:32
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    $\begingroup$ I expect them to be quite skilled with small arms. $\endgroup$
    – user20762
    Oct 30, 2017 at 13:59

25 Answers 25


Of course it would provide an advantage. It would provide a lot of nice advantages in fact.

I can tell by most of the answers that the people writing them have been as close to combat as maybe their copy of Call of Duty, so I thought I'd give a little perspective.

An elite squad with unique abilities sounds a lot like an SF team to me. Special Forces means doing a lot of things that CANNOT be replaced by a drone with a hellfire missile (in other words, lots of non-kinetic stuff). While SF teams obviously do train for kinetic situations and are really good at dealing with them, their primary use is NOT to engage a major enemy force head to head. I repeat: a modern special forces team is NOT a front line infantry unit (as most of the answers here obviously assume).

So what does that mean? Well, they might be jumping out of an aircraft at very high altitude, drifting over a national border with steerable parachutes, silently landing in the dark at a designated point, hiking to a target, camping out invisibly in the woods, and just watching the target for a week or so. They might be looking for intel on some specific bad guy, or they might need to ID what exactly somebuilding is being used for. They might then later have to "paint" that target with a laser that guides the 500 lb bomb let go by an F-15 or something else. Then, they might have to hike out to an extraction point without being seen. In such a mission, they would ideally NEVER have to engage in direct action against the enemy force. Would being able to become a T Rex be useful? Well yeah; the hike out would sure be a lot faster if you could run over 30 miles an hour! You could also carry all sorts of stuff that might be too heavy for a regular soldier, but which might include concrete proof of the state of the enemy's WMD program or whatever they are looking for.

Modern SF teams always have a problem when they come across potential prisoners who they could capture but who they didn't plan to encounter. They travel light and they don't have a lot of reserve for carrying extra stuff (like 200 pounds of bad guy with good intel in his still-living head). If they do encounter someone who would be a good captive, they have to make a fast judgement and figure out if he's really worth capturing or if they should kill him or turn him loose. If one guy could turn into a T Rex, they could literally incapacitate him, clip him to a harness on the 'rex, and carry him out if they thought he was useful.

Modern SF teams use ATVs and modified dune buggies in open terrain. They have used horses to get around (like when we first went into Afghanistan). Being able to turn into your own fast moving vehicle would be very useful, especially since you don't need to carry fuel. One guy could carry the rest of the team and they could cover him while he transformed back and put his gear back on. Any open area that is not a dense city would make this useful.

Basically all of the "getting there" and "getting out of there" parts of the mission would be excellent times to have a T Rex on the team. TO maximize this mobility, it would probably be best to spread out your 'rex soldiers among teams of regular operators so you can have many teams able to use a 'rex for transport. Say if you have 10 of these guys, you would put together ten teams with one on each, and the other guys specialized in other things like language, pilot skills, medic, explosives, etc.

So lets say you are in a kinetic situation. There are things that your T Rex soldier would be good for. Say you are out on an open desert. You have an enemy at extreme range and you need to slow them down while the rest of the team starts to get away. You transform your guy, set a sniper up on his head, and use the height advantage to help your sniper kill enemy soldiers from farther away than they can kill you. That's kind of an edge case, since obviously a 'rex is a big target, but having an instant firing platform can be useful sometimes. Your 'rex can also become an instant elevator to lift his team mates up onto a roof (we did a LOT of climbing up onto roofs when I was infantry).

So, worst case scenario, your small team has to actually get into it. If you are ready for it (which I assume you are, since these are elite soldiers, not idiots), you have some battle gear for the 'rex. You might have this bundled and dropped by parachute, or the 'rex can pack it in on it's back and then leave it somewhere while in dude mode, and go back to his 'rex gear when he needs to get outfitted, or he could stay in 'rex mode for the duration of a mission depending on how long it is going to be and just wear his kit like everybody else. The point is: there would be battle gear for the 'rex just like there would be for the other guys.

In today's world: we have reversed the Napoleonic paradigm, we just don't know it yet. Materials technology has actually developed armor that can stop typical infantry weapons and can be worn by a normal person. Ceramic plates will stop a 7.62 mm NATO machine gun round, which is really impressive. The only reason we haven't gone back to the old "knights in armor"/Starship Troopers paradigm is because this kind of armor is too heavy for a guy to carry and run and climb and also carry weapons, supplies, etc. This is where it's nice to have a T Rex around. You could have ceramic plates built into the 'rex kit that make him basically a light armored vehicle, except unlike any vehicle, he can also roll, duck behind a building, jump onto a roof (a big, heavy roof), smash his way inside a building, dig himself a trench he can take cover in, etc etc etc. It wouldn't be hard to have a couple useful weapons he could strap on his arms and use a simplified trigger mechanism with either. Heck, he could have a .50 cal machine gun integrated into a headband and hit a trigger with his tongue... You really have a lot of options with something that big. Probably best would be some kind of vehicle-mount deal too big for anyone else to carry that would give your team a real advantage in firepower. I don't know, what about a 20mm anti-material rifle? A 'rex could actually haul that around!

Basically, you get the armor and firepower of a vehicle with almost the flexibility and stealth of infantry. I guarantee a smart T Rex is a LOT quieter than an MRAP when he wants to be. Like I said, he'd also be able to get down on his belly and wriggle behind a low building or a wall for cover, unlike any vehicle ever made. So your team has some emergency heavy backup in case stuff goes sideways. He would also be pretty survivable. He would have to take a couple hits from an RPG to die with the right armor kit.

About some of the estimates of how easy it would be to take down a T Rex with a modern firearm: I think a lot of these people answering have never hunted for big game in their lives. Look up forums where people talk about shooting a charging bull moose or a bear. They do NOT carry rifles with the kinds of caliber used by most infantry weapons! An M-4 is basically firing high-powered, tumbling versions of slightly bigger .22 rounds. This is great for chewing up a soft target roughly six feet tall and about 200 lbs, but it SERIOUSLY falls short the second you try to take down anything bigger! You try taking your M-4 up against a bull elephant and all you are going to do before he stomps you to death is piss him off real good. You put it on full auto and other than missing with half your shots, you just piss him off more, because not he has a lot of "bee stings" in his hide. More rounds do NOT mean more penetration! A T Rex, with a bone structure sort of like a crocodile, would take some VERY heavy rounds to actually penetrate anything vital! I doubt a 7.62mm NATO round would do much. You would have to rock him with a .50 cal machine gun to actually stop him. Either that or hit him with an RPG or two. The problem with an RPG is you get 1 shot at a time, they aren't fantastically accurate, and they aren't designed to hit things that zig zag, roll, or dodge. They were designed to hit the side of a tank!

So even if he was NOT wearing armor, (which he would be), the Rex would require an elephant gun to reliably bring him down. Normal infantry units do NOT carry weapons like that!

Once again, think about the largest crocodile ever discovered and multiply that by about 5. Now think about hitting it with a pea shooter like an AK. It just won't work out too well for you.

In summary: it would be VERY useful for a wide variety of reasons (I didn't even get into my favorite scenario: jungle warfare!)

  • $\begingroup$ I've accepted your answer, but as a follow up, would you modify it at all if it were the case that the strength of a T. Rex's bone structure is more proportional to that of a turkey than a crocodile? $\endgroup$
    – JNW
    Nov 3, 2017 at 21:02
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    $\begingroup$ No. A 30 foot turkey would be very formidable. In fact it would be pretty terrifying. Emus are extremely dangerous animals and they are barely 5 feet tall. A bird the size of a rex would be a nightmare. Maybe without the kind of bony plates that a Croc has, you might be able to get more penetration with smaller caliber rounds, but it is still a fact that infantry weapons are specifically designed to take down something about six feet tall, not something 20-30 foot and weighing multiple tons. An M-16 or an AK-47 are basically pea shooters to that thing. $\endgroup$
    – JBiggs
    Nov 4, 2017 at 2:19
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    $\begingroup$ @JBiggs you would put together ten teams with one on each, and the other guys specialized in other things like language, pilot skills, medic, explosives, etc. Don't forget the paleolithic veterinary ! $\endgroup$
    – Legisey
    Nov 17, 2017 at 14:33
  • $\begingroup$ @frouil LOL If you believe Jurassic Park, maybe a "chaos theory" scientist would be helpful as well. ;-) $\endgroup$
    – JBiggs
    Nov 19, 2017 at 1:39
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    $\begingroup$ @JNW Considering that Australia lost a war against Emus, I'd say that a 30 foot tall turkey would be damn terrifying. $\endgroup$ Jan 30, 2018 at 10:40

I can imagine battlefield logistics would be much easier. One of the most dangerous and common tasks for infantry is shuttling supplies back and forth between the front lines and the forward camp. If you could load up a huge pack with crates of ammunition or even vehicles, the "runner" could transform into a T-Rex, run the munitions up to the front, and transform back, being unhindered by terrain that a Humvee might have issues with.

However, in modern warfare, prolonged front line infantry fighting is becoming more and more rare, only happening in dense urban areas where a T-Rex would be a liability or when one group surprised the other. Most kills happen at pretty extreme distances nowadays.

There could be a use in peacekeeping efforts, since nothing says compliance quite like a >12 foot tall dinosaur.

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    $\begingroup$ This answer is brilliant. ‘Would T. rex soldiers be useful?’ ‘Yes, but not for the reasons you might expect...’ $\endgroup$
    – Joe Bloggs
    Oct 27, 2017 at 18:51
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    $\begingroup$ Don't forget what an awesome recruitment tool this would be. :) $\endgroup$ Oct 27, 2017 at 21:54
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    $\begingroup$ I'm selling fences and generators anyone? Order now and receive a T-Rex spray... $\endgroup$
    – user6760
    Oct 28, 2017 at 4:06
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    $\begingroup$ Am I the only one who's wondering just how much damage a modern rifle would be able to do to a T. Rex? This is a creature that's quite a bit larger than an African Elephant. $\endgroup$
    – Clearer
    Oct 29, 2017 at 17:36
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    $\begingroup$ There could be a use in peacekeeping efforts, since nothing says compliance quite like a >12 foot tall dinosaur. "If everyone complies with our instructions, we'll let you ride the dinosaur." $\endgroup$
    – Ray
    Oct 30, 2017 at 14:20

Stop thinking shock troops.

Think strategic asset and later assassination.

To start with, while your were-Rex's are still a military secret, hand them over to your espionage department and get the trained in the languages and behavior traits of your target enemy nation. Then get them behind enemy lines and integrated into your enemy's civilian populace. They don't need to get to anything sensitive yet. They just need access to public gathering places.

Now, in the hours before your next major assault, have two or three of them gather in a subway central station or a big shopping mall. Have one of the team transform and start slaughtering random citizens while running quickly through the complex. Each time, the creature manages to obscure itself around a blind corner or in an empty hallway, have them transform back to human and signal a team mate in another part of the station to take the leading reptilian role.

Mall security guards will quickly realize that they are outmatched and will call the police. The police will also soil their pants before calling the military. The military will have to take key defensive resources away from your targeted (valuable) strategic target, in order to go deal with the Godzilla attack. And as soon as those resources arrive at the mall, your were-Rex team will all switch back to human, escaping among the panicked crowds.

Then while the enemy military is searching the mall for dinosaurs, your regular military can easily take out the undefended valuable target.

This technique would only work a few times, maybe only once. But after that, your were-Rexes could split up and become one-man terrorist cells. No normal security scan could find the weapon which they themselves are. The possibilities are endless...

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ Oct 31, 2017 at 2:52
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    $\begingroup$ So the military will be called in to handle the T-Rex'es and the streakers! Even better. @ThisClark, discussion of the shortcomings of this answer (including your concern for the PG rating of its film-adaptation) has been moved to chat. $\endgroup$ Oct 31, 2017 at 17:35

No, because they cannot take their equipment with them

Your average modern NATO-type infantry soldier is skilled at hand-to-hand combat, but that's used as the last resort.

Ideally, the enemy is dead, captured, or defeated long before they reach tooth-and-claw range. NATO-type armies fight in depth and synchronized, with many services and branches fighting across a battlefield hundreds of kilometers across and deep in support of a single set of objectives.

Non-ideally, the enemy can hide (often among civilian populations) to ambush and strike at short distances against fairly small friendly targets. Those friendly targets rely upon armor and upon immediate, strong artillery and air support to make up for the enemy's surprise.

Infantry soldiers carry equipment in support of both fighting styles that T-Rex simply cannot use nor even carry in their dainty little hands:

  • Rifles/Carbines with an effective aimed-fire range of up to 500m
  • Automatic weapons with maximum ranges from 600-1000m
  • Indirect fire weapons ranging from 150m to 2 miles
  • Radios capable of calling in artillery, close air support, air strikes, naval gunfire, EOD, MEDEVAC, etc.

Without the equipment, the T-Rex is simply a standalone close-in fighter, not an element of an Army...and more likely to become a casualty as a result.

T-Rex isn't bulletproof or RPG-proof, is surely incapable of defeating a 40-ton Tank (or surviving a roadside bomb), and isn't fast enough to outrun artillery. Note that soldier could not change to/from a large T-Rex from inside the protection of a (cramped) armored vehicle

There are a few advantages to, say, a 12-foot T-Rex that is capable of also firing weapons and using radios, but those are obvious.

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    $\begingroup$ A bit of well observed common sense there. Also if this transformation ability was known in advance, the troops facing it would be prepared mentally and tactically. I can't help thinking they'd have weapons designed for downing a T-Rex at distance. $\endgroup$ Oct 27, 2017 at 18:56
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    $\begingroup$ @ Joe Bloggs I think a T Rex would come out very much the worse in an engagement with a tank. Armoured steel hull v flesh and bone... $\endgroup$
    – Slarty
    Oct 27, 2017 at 18:59
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    $\begingroup$ @JoeBloggs I think the current non-T-Rex methods of incapacitating or destroying tanks, while much less romantic, are more likely to succeed. AT-4s are simply not that expensive, and cost much less than the SGLV on the T-Rex. $\endgroup$
    – user535733
    Oct 27, 2017 at 19:06
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    $\begingroup$ @slarty disagree, tank weapons are useless unless they can hit the target. If T.Rex knows he's fighting a tank, he's way too agile to get hit by a tank round, so the tank is down to spray-and-pray with their small gun(s). T.Rex just gets inside the tank's minimum fighting radius, chomp the small guns off, and now it's a ring match. If he can carry even one satchel charge in his little arm, it's a super one sided fight. $\endgroup$ Oct 28, 2017 at 23:05
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    $\begingroup$ @Harper tanks generally carry co-axial machine guns alongside the main armament, that can traverse quickly and quickly turn a T-rex into a large helping on dinosaur pate. $\endgroup$ Oct 29, 2017 at 18:30

A squad of T-Rex shapeshifting soldiers would have some advantages but depending on the exact circumstances these would almost certainly be dwarfed by the disadvantages.

The shape shifters would have a huge surprise, shock and disorientation value initially.

They would be difficult to camouflage, they would present very large targets, they would be relatively easy to kill with machine gun fire, automatic rifle fire and perhaps even large calibre pistols. They would be vulnerable to mortar and rocket fire, land mines and attack from the air. A tank would be able to kill a T. Rex by simply ramming it.

Shape shifters would also become naked each time they returned to their original size or would have to undress and dress again. Such an effect could cause serious problems in extreme environments such as deserts (although it might amuse the enemy).

Their size would prevent them from effectively taking cover. In open terrain they would be sitting ducks and close terrain would probably provide a more nimble enemy with better escape and avoidance options.

  • $\begingroup$ Add to this: they are very vulnerable. A heavy creature might more easily break a leg if it mis-trod. $\endgroup$
    – Stilez
    Oct 28, 2017 at 22:00
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    $\begingroup$ About the becoming naked, I think you can argue that it's not a problem. If it's already acceptable to think that this soldier is capable of reshuffling his body's materials (and increase/decrease the mass of his body) in order to shapeshift into a T Rex, it's not unthinkable that he's able to reshuffle his overalls into a little pouch somewhere, and later reshuffle the overalls around his body again. The main difference here is that the T Rex is different (which suggests molecular recompositioning), whereas e.g. The Hulk merely expands (and thus rips his clothes). $\endgroup$
    – Flater
    Oct 30, 2017 at 10:04
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    $\begingroup$ To finish my thought, the T Rex likely has a different skin/skeletal structure than the human, thus suggesting that the human does more than only growing in size by shapeshifting. If he's already changing the physical structure of his skin and bones, he should use a "fluid" state inbetween the shapes he shifts between. He should then also be able to shift the overalls into a pouch as well. $\endgroup$
    – Flater
    Oct 30, 2017 at 10:06

Awesome for morale!

Fighting T-rexes would not be worth much against automatic weapons. But T-rexes are freaking awesome! Think of how fired up the folks at home would be to see a bunch of soldiers suddenly explode into Trexes. They could roar the National Anthem then grab blood-filled mannikins of enemy soldiers and shake them like a dog shakes a squirrel! The Trexes could come out painted in patriotic flag colors, ridden by comparably dressed models, shoot off special Trex-sized guns, and then dance to popular music.

Best of all would be if the soldiers could transform partly into Trexes, so one would have a Trex head on a mans body, another a mans head on a T rex body... Or maybe that would be too freaky. OK not that.

I am thinking of Captain America where they (correctly) determined the best use for a supersoldier was in public relations, to boost morale of the folks at home. I think also of the electrical zombie-exploding machines described in the (book) World War Z - pretty much expensive and worthless for fighting zombies, but a guaranteed crowd pleaser.

Yes, singing, dancing, biting, roaring patriotic T rex soldiers would be awesome. I can imagine that the crowd favorite Trex soldier winds up running for office after his military career. You know he would be elected in a heartbeat. I want to vote for him now!

I was surprised how many great videos of dancing Trexes there are.

  • $\begingroup$ Until they are dead. What's the morale value of a fragged TRex...? $\endgroup$
    – Stilez
    Oct 28, 2017 at 22:01
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    $\begingroup$ @Stilez: You never send these guys into harms way. The closest they would get would be a USO show. $\endgroup$
    – Willk
    Oct 29, 2017 at 17:14
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    $\begingroup$ "And then the UN un-nazied the world!" i.imgur.com/9VfHd5T.jpg $\endgroup$
    – Headcrab
    Oct 30, 2017 at 5:31


One M203 Grenade Launcher, firing at 160 meters away, will quickly turn the elite troop into goo.

From 800 meters away, an M240 Machine gun, can fire 950 large 7.62×51mm rounds a minute. The T-Rex would be swiss cheese before it could touch a claw on the modern soldier.

These are standard infantry weapons. I shudder to think how a T-Rex would stand up against an Apache or an M1 Abrams.

  • $\begingroup$ I shudder to think how a T-Rex would stand up against an Apache or an M1 Abrams. If it were smart, it wouldn't. Then again, T-Rexes were reputed to have tiny brains... $\endgroup$
    – nzaman
    Oct 28, 2017 at 5:53
  • $\begingroup$ Presuming a T.Rex would stand still for the travel time of an RPG or the flight time of a bullet at 800m. Mobility would be everything for a T.Rex. Now, T.Rex vs Apache, that'd be a fight. $\endgroup$ Oct 28, 2017 at 23:11
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    $\begingroup$ The flight time of a bullet at 800m is in the order of one second, and there will be more than 10 of them per second coming out of the MG. Given that a T-Rex will be less able to dodge than a human - along with being a larger target and less able to hide - it will have no chance of dodging the incoming fire. $\endgroup$ Oct 29, 2017 at 22:31
  • $\begingroup$ @Matt Bowyer But it can wear an armored apron! $\endgroup$
    – Headcrab
    Oct 30, 2017 at 5:33
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    $\begingroup$ An M203 grenade would also turn a soldier (likely more than one) into goo as well. The T rex is a larger target, but also requires a grenade per T rex. Your enemy's army's logistics would have to ferry around grenades like a modern military ferries around bullets, thus making it a more cumbersome task. And then you can exploit that weakness by blowing up their crates of grenades (as opposed to crates of bullets). So you could gain an advantage by being able to transform into a T Rex (= enemy must bring many grenades), without actually having to transform into one. $\endgroup$
    – Flater
    Oct 30, 2017 at 10:20

They would just make great targets. As ferocious as a T-Rex might seem, a single anti-tank missile would take one down very quickly, by blowing a huge hole in it. A dozen rounds from an assault rifle would at least cripple it, probably kill it. That assumes one is facing a modern military, who tend to be disciplined and trained enough to get over the shock value of seeing a T-Rex appear.

The most effective soldier today is the one that makes the most effective use of modern weapons. A T-Rex would have a tough time working modern weapons systems.

  • $\begingroup$ This. A T-rex is fearsome in melee--but how much melee occurs in modern combat? Virtually nil. Otherwise, they're just bigger targets. $\endgroup$ Oct 30, 2017 at 4:35

T-Rex would be good in special missions. For example, counter terrorism. You have a building and the enemy is holed in it, and your T-Rex private can break doors, walls and help the other troops get in. Or, you could send a negotiator T-Rex to your terrorists holding hostages. Once it gets in, your negotiator turns into T-Rex and starts chomping on terrorists. Terrorists won't know what's going on, and they'd be too busy shooting at the dinosaur to kill the hostages first.

Another great use for T-Rex soldiers is assassination missions. You get your spy close to the enemy leader, he turns into a T-Rex, bites the enemy's head off, then turns into a naked dude with PTSD.

Breaking off protests is also an interesting use of T-Rexes. When the citizens in your capital protest against the government selling, yet again, your country's forests to Austrian evil billionaire, instead of police, you release the godzilla-boys into the crowd. They kill as many as they want and the protesters will know next time that it's government who owns people, not the other way around.

It goes without saying that T-Rex soldiers would be great for ethnic cleansing. The international community would be ready to believe, for the correct price, that jungle beasts, fed up with the loss of habitat, took revenge on the minorities, for it is known that in every country, if things are bad, it is because of the groups who lack the numbers to defend themselves. The numerous photos and videos on facebook would document this. The National Guard will show up to deal with the threat, and will shell the area, until the houses of the offending minority would be all but destroyed, and people who did not take the hint would be killed.

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    $\begingroup$ Might be a handy way of smuggling in a deadly weapon, at least. $\endgroup$ Oct 29, 2017 at 22:32

Of course it would be useful, but probably not very. "All that and a bag of chips" is always better than "all that," so if you can have the option of dinosauring out for free, you should always take it.

In general though, I would not expect a small population of were-asaurus rexes to make a significant difference to a modern army, in exactly the same way that I would not expect access to elephants to make a significant difference.

However, if a significant fraction of your forces can turn into 25-tonne carnivores, that might change things. If nothing else, your force-protection posture would look pretty different.


Would be useless in direct modern combat, their huge size would play against them (basically, all the disadvantages of a modern tank without any of the advantages). The last wars they could've actually fought efficiently were probably some time around Napoleonic era. E. g. big organized formations, charging cavalry, bayonet attacks etc. - the T-Rexes probably already could not just win any battle by simply charging ahead (they make too good targets for muskets and cannons), but with some clever flanking or in the right situation could still wreak havoc in the enemy lines.

Now they might still have some specialized and limited use. By today's estimates they were able to walk at about 20 km/h (12 mph). Not as good as a car or an APC on a road or good, flat terrain. But how about some deep raids into the enemy territory? Through bad terrain, mountains, jungles, swamps, etc. With some equipment strapped to your back and maybe a group of more conventional soldiers riding along? Need to cross that little river swarming with crocodiles? Not a problem.

There are still some questions, though. How much do they eat? When it's lunch time, can a dinosaur simply transform back into the human shape, eat an ordinary human ration and transform back "for free"? Or does it have to catch a couple of buffaloes each time? What if the dinosaur catches some "T-Rex fever" - would it affect his human incarnation? Can such a soldier safely walk through malaria/plague/ebola/whatever -infested territory in its reptilian form? If a dinosaur gets, for example, shot with a small caliber handgun, or receives any other damage he can just "shrug off" - does that become a problem when he morphs back into the human shape? What if its T-Rex's tail gets blown off with an explosion? What about the momentum conservation? Let's say I am an 80 kg human, transform into a 8000 kg dinosaur, walk in some direction 20 km/h and morph back while walking - do I rocket in the same direction at 2000 km/h now? How tired do I get in both forms? Am I cold-blooded (can function at sub-zero temperature; invisible to heat-seeking tech)?


Many answers have been given. They are good answers, considering different perspectives, but I think that most objections can be solved when you observe the current context.

Since we're talking about the impact of shapeshifting soldiers on a modern military, I think we can make a few other rules:

  1. Anything less crazy/advanced than a human shapeshifting into a T Rex should logically be allowed.
  2. Anything that is based on scientific principles that the shapeshifting itself relies on should logically also be allowed.
  3. Shapeshifting into a T Rex becomes useless if the benefits of doing so can be achieved by using cheaper and simpler methods (e.g. comparing it to a tank).

I'll refer back to these rules as justifications for later statements.

There are many things to consider here, I'll try to address all that I can think of.

1. Shock effect.

While the shock effect will indeed work, this will be temporary. The enemy will get used to it, they will prepare their troops, they will arm themselves appropriately (thus lowering panic from being unprepared)...

There may be some residual shock from seeing a T Rex charge at you (a basic fear instinct), but any adequately trained soldier is trained in suppressing their instinctive responses to fear.

2. Open warfare.

I think there is little benefit to be gained here, compared to what armies already have available.


  • Destroying buildings (rule 3: you can use a tank or explosives)
  • Bullet sponges (arguably not a benefit, it expends super soldiers which may financially bankrupt your military) (rule 3: you can use a tank or something like a riot shield)


  • Massive target
  • Likely unable to wield any weaponry nor armor (since that would require a soldier carrying around T Rex sized armor)
  • Limited to melee range

Due to their melee range and massive size making them an easy target, this is the equivalent of taking a knife and no ballistic armor to a gunfight.

3. Infiltration.

This may actually yield a benefit. One of the major issues with infiltration missions is that you need to pack light. This means that if you are spotted, you don't have much equipment to defend yourself.

Infiltrations take place in places that are heavily defended, but generally are not actively in combat at the time of infiltration. This means that a tactical strike may allow a T Rex to wreak havoc and shapeshift out of sight before the guards have a chance to counterattack.

Fringe scenario
This is more a question for you: what happens if a soldier shapeshifts into a T Rex when he is in a small room? Do the walls collapse? Does the soldier fail the shapeshift? Does the soldier die because he can't achieve a full form (that is biologically sustainable)?

If the soldier breaks the walls, you could have your soldiers let themselves get captured, only to then rip the inside of the enemy compound to pieces. Even if you don't intend your soldiers to get captured, this seems like a dramatic upgrade from e.g. a cyanide pill: your soldier still dies but has also massively damaged the enemy's compound.

4. Shapeshifting problems.

The biggest issue that the answers have raised is that you'd be naked when you shift back into human form. I don't think this is necessarily the case. I can see two arguments here that make sense.

Firstly, the soldier could wear a custom material that can deal with the transformation. If your soldiers are capable of shifting back and forth without issue, I would expect that your scientists have been able to create a material that can sustain a similar repeated in/decrease in size.

Rule 1: If you can already make living tissue deal with size changes, you should definitely be able to find a non-living material that can handle the same thing.

_Other fictional universes have solved this by making a special material that responds _just like your own living cells__ when a transformation starts. I.e. your body's cells cannot see a difference between themselves and your body suit's cells, thus including them in the shapeshifting process (whatever happens to your body's atoms also happens to the suit's atoms)._

Secondly, your soldier may be able to "store" his (non-shifting) apparel. Your T Rex shapeshift isn't just a matter of increasing/decreasing in size (e.g. like the Incredible Hulk). Your soldier is physically altering the structure of his body. His skin and skeletal structure will vastly change.

Rule 2: If your soldier is already capable of reconfiguring his own molecular makeup, he should be equally capable of reconfiguring his molecular makeup in order to account for his apparel. Since he's already changing his molecular structure, he could morph his body around the suit, thus storing it internally in the T Rex' body. There are a few ways this could be achieved:

  • If your soldier is capable of shifting his insides around (molecularly), he should be able to shift the apparel into a little pouch somewhere.
  • If your soldier is not capable of shifting his insides around (molecularly), then it's possible for the apparel to stay in place. E.g. if the human soldier is the right leg of the T Rex (and the rest of the T Rex body grows from there), then the apparel might still be inside the T Rex' right leg.

5. Logistics.

You have a double whammy here.

The first one is relatively simple: Most armies are limited by their logistical capability. Having your soldiers transform into T Rexes is the logistical equivalent of having your soldiers transform into (fuel-free) transport trucks. It pretty much solves all logistical problems (at the cost of being less armored and more visible).
Rule 3: when you really need armored vehicles or don't want to draw attention, simply use whatever you were using before the advent of the T Rex super soldier.
Rule 1: Or you could simply develop an armored suit for your transport T Rexes.

The second one is more insidious.

Remember how I mentioned (in chapter 1) that the enemy will eventually prepare to battle with T Rexes? One answer here correctly pointed out that an M203 grenade would make short work of a T Rex. And that is correct. However, do not that you'd need at least one grenade per T Rex.

That means that your enemy needs to have a massive amount of grenades available. They would essentially need a grenade for every potential T Rex that you bring into battle (and that's not even including missed shots, extra supplies, or lost ammunition).
This will massively affect your enemy's army's logistical capabilities. Grenades are much larger than bullets (obviously), and need to be handled with more care. Both of these will lowers the amount of grenades that their logistical system can provide to a region.

Your enemy will then be less eager to engage you in combat if they don't have an adequate supply of grenades, which is harder to come by than bullets. Secondly, this makes their warehouses more explosive (due to many more grenades), which can be a weakness if you target their ammunition stores.

Logistically, this does make sense.

6. Playing your enemy.

I watched an episode of a Cops-like show yesterday. The cop made a valid point when he was unable to catch a fleeing thief on foot.

Criminals come in all sizes. Slow and armed, fast and unarmed, defensive, offensive, carrying chemicals to disable officers, willing to kill, ... Police officers need to be prepared for all situations. Criminals only need to be really good at one of the situations to win. Cops are at a disadvantage because they have to be a jack-of-all-trades, and therefore are unlikely to outmaster a criminal in a particular field (other than sheer numbers).

The same tactic is true here. The fact that your soldiers are able to shapeshift means that your enemy needs to prepare for that eventuality. But that doesn't mean that your soldiers are required to actually shapeshift.

Even if there are countless drawbacks and only one fringe case where shapeshifting grants a tactical advantage, that means your super soldiers are still capable of assessing whether or not they should actually shapeshift. It's a tool in their arsenal that they can choose to use.

Unless these super soldiers have a weakness (in human form) that non-super soldiers do not have, there is no drawback to having the ability (other than the financial ramifications of turning them into super soldiers, of course)

7. Patrolling and surviving the elements.

Are your T Rexes capable of anything a T Rex is? Because that would make them useful for patrolling large regions.

They could even rely on eating local wildlife rather than having to take provisions if you send them into a large jungle/forest.

Given that they retain their human intelligence, that also means that a super soldiers is able to shapeshift based on what suits them best:

  • Cold weather? Stay in human form, you're warm-blooded.
  • Hungry? Become a T Rex and hunt wildlife.
  • Enemy soldiers trying to stay hidden? Have your squad go half human and half T Rex; the enemy will need to avoid two completely different types of enemy in order to stay undetected.

8. No cheesing.

Not a real chapter, but I wanted to list things that I omitted not because they wouldn't work, but because they are too cheesy for narrative purposes:

  • Utilizing the mass difference between a human and a T Rex to cheat physics. E.g. imagine balistically launching a human (low-energy) but having him land as a T Rex (high-energy).
  • Similarly, no power generation or other ulterior benefits from the change in size/mass.
  • Other than the shapeshifting itself, no superpowers that T Rexes and humans do not have. Also, humans are limited to human capabilities, T Rexes are limited to T Rex capabilities (no speaking T Rex, no human that can bash through a building)
  • No mysterious animalistic skill whereby a T Rex can expertly command other animals. This would also violate rule 3, there's likely a much cheaper way to coax animals (e.g. build a fake but convincing T Rex model).

9. Summary

In essence, there are benefits to having T Rex shapeshifters. However, they are not likely to be found in open combat, but more in the auxiliary aspects of a modern day army.


If you can do a T-Rex, why not other Theropods?

Load up your were-dinos in specific roles, depending on Dino Type. The T-Rex can get to places a Tank might not, so he'd be good for Crowd Dispersal and work in public square type stuff. Something like a tank would be superior in realms like sheer destructive capability, but they are not as good at fine control. The tank could easily take out the rabble rouser on a makeshift stage, but it would also take out the stage and a bunch of collateral damage is done. The Rex could lean down, chomp, and done. Appear, munch and go away. or maybe appear and then just throw intimidation factor at the crowd.

For more modern warfare type stuff, smaller, human sized Dinos would be better. Think Deinonychus, which I believe the "Raptors" from Jurassic Park are based on. Not a lot bigger than a human, but much faster, much more agile. Weapons could probably be modded for them to carry and use, or even in a way that would be useful in Dino or Human mode without needing tools. They would be able to get into buildings, caves, etc. They would be fast, and they would likely be fairly quiet. I'd be willing to bet that a normal soldiers loadout could be rigged in a way that you could ditch the ruck and unzip the back of your pants to let out the tail. Transform, get the ruck back on, and go. Imagin this from an enemy standpoint. You are holed up, you see some human enemy soldiers come in to the cave, lights go out. Next thing you see is a monster with lots of teeth and huge claws ripping up your buddy. How terrifying would that be?

They could also cover ground quickly where a tank or Humvee would not be able to get through, like jungle or swamp.

In Short, T-Rex for big public duty, but Deinonychus for the real fight.

  • $\begingroup$ Upvoting for everything covered in JBiggs's answer, only without having to scale the equipment up for a huge creature. $\endgroup$ Dec 31, 2018 at 16:17
  • $\begingroup$ Just a comment: your answer is good, but Deinonychus are dromaeosaurs, not theropods. $\endgroup$
    – Alendyias
    Jan 30, 2021 at 22:37
  • $\begingroup$ @Alendyias Taxonomy was never my strong suit. I've always associated two legged carnivores with Theropods. $\endgroup$
    – Paul TIKI
    Feb 3, 2021 at 18:25
  • $\begingroup$ Fair enough, no offense intended. They are pretty similar, both being bipedal carnivorous dinosaurs and all. $\endgroup$
    – Alendyias
    Feb 3, 2021 at 19:00
  • $\begingroup$ @Alendyias No offense taken at all. TBH most of my knowledge of Dinosaurs comes from a set of childrens books and, of course, Jurrasic Park :) $\endgroup$
    – Paul TIKI
    Feb 4, 2021 at 21:15

While the kill-the-civilians-as-a-distraction approach is a war crime I can see other uses for them in a special-forces role:

1) Team infiltrates a wooded park that's not too crowded. Member A dons some tough armor that isn't apparent, he's in the park on the outskirts of a crowd. Member B goes into the woods, transforms, runs out and grabs A who screams and releases some blood but due to the armor isn't actually hurt. After dinosaurs have "eaten" a few people don't you think the clamor for protection will be just about deafening? And there's sure to be more "victims" that simply use the dinosaur as a cover for dropping out of sight.

2) Sabotage. That oil refinery had reasonable defenses against human intruders. When they mug a worker and replace him with a T-rex, though, and he runs around breaking pipes you have a lot of damage. Lots of flammable hydrocarbons on the ground when someone pushes the button and a bunch of low-grade aerial fireworks get lobbed over the fence. (Simply tip the launchers so the average burst point is a few feet above the ground.) They couldn't get into things like the control center but they don't need to.

3) Infiltration. A pair of T-rexes can cross barriers that an unaided human could not. As with the oil refinery this means they can get past security and then do where they shouldn't be able to. (If you know nobody could have a ladder you'll consider a 6' razor-wire fence a pretty good barrier.) I'm thinking of areas that have high security surrounded by low security.

4) Infiltration over long distances. A T-rex team would have a lot longer self-supported travel distance than a human team and would be better at hunting without the use of firearms.


You should think about the characteristics of a T rex and wonder how useful they would be...

In a quick search, I got this:

T. rex was one of the largest carnivorous dinosaurs to ever live, coming in at up to 13 feet (4 meters) tall at the hips (the beast's highest point since it did not stand erect) and 40 feet (12.3 m) long. (...) weighed as much as 9 tons (about 8,160 kilograms). (...) had strong thighs and a powerful tail, which counterbalanced its large head (the skull is 5 feet, or 1.5 m, long) and allowed it to move quickly. (...) could run 10 to 25 mph (17 to 40 km/h) (...) powerful bite and a mouth full of serrated teeth (...)

I don't believe thoso skills would be enought to fight the enemies's guns

  • 3
    $\begingroup$ The only answer that actually gives details on what a T. Rex actually is, and it's being downvoted. Shame. $\endgroup$
    – Clearer
    Oct 29, 2017 at 17:33
  • $\begingroup$ @Clearer Because the answer doesn't provide any good explanation why any of these abilities would or wouldn't be useful. It's a shame it got any upvotes. $\endgroup$
    – Philipp
    Oct 30, 2017 at 12:40

No. As others have already pointed out, perhaps the greatest thing about it would be the element of surprise. However, assuming that in your world, dinosaurs are extinct just like they are in reality, the very presence of them would be more than suspicious -- combined with the fact that they just happen to be wandering around military facilities would quickly reveal what is going on. So on the first few occasions, yes, they might prove useful depending on the circumstances, but as soon as the trick is revealed and the enemy becomes aware they do more harm than good because of their size, lack of camouflage, inability to handle tools, etc.

Given the fact that in your world, people have the ability to shapeshift into something else, and what's more, into a dinosaur, I believe it would be way easier and more beneficial to turn into something else -- something that rather than calling out for attention, right the opposite, can be stealthy. For example:

  • Bombarding birds: very obvious, turn into birds, and drop tiny bombs onto the enemy. Before they realize what's going on, they are sweeped down.
  • Bacteria/poison delivery insects. These substances could be lethal in the tiniest of amounts, which could be easy to be carried by such small beings.
  • A small mammal, for eg., a cat: very common to see in most environments, not suspicious. Could even hide a razor in a pocket stiched under the skin and cut the throats of an entire regiment overnight without notice.
  • Snakes, spiders, scorpions, etc.: use what nature already provides - poison. Can be suspicious after a series of bites.
  • Anything that is common in the operating environment and preferably has the ability (properly structured hands, for example) to use tools.

I do understand that these are a little off topic, but I think it is completely irrational to be able to invent a way of turning into a dinosaur but not into a common cat.

Also realize that this is a double-edged weapon. Sooner or later, the enemy finds the dirty trick out and use it against you as well. It is sometimes better to secure such inventions until the very last minute they are needed -- always assume that given the fact that you've discovered it, it is possible, prepare for the worst and hope for the best. The reason is that once it is found out, you can no longer trust anyone and perhaps this would be the mindset of a rational enemy who at least generally adheres to certain moral standards of warfare.


Oh man, the only real answer is TOTALLY YES!

People here are overlooking the most significant aspect of the scenario:

(let’s say the process takes 1-2 seconds).

Without this is still viable, but this alone provide a significant advantage: SPEED.

Let's build scenarios that were ruled out because supposelly a T.Rex was at disadvantage in modern warfare:

  • What about Jets, Rockets and heavy ammo? What do soldiers today, that are not T.Rex? Them BRING HIS OWM.

But now, this soldiers ALSO ARE T.Rex.

  • You elite squad is still a elite squad. Them will not do stupid things.

Them are smarter, but also ARE T.Rex. Them will know that a static target is death. Them will use speed as advantage. And a T.Rex is faster and more agile that some vehicles/machines.

So, any advantage a elite soldier have, plus being a T.Rex mean a total net win.


  • You can shapeshift in 2 seconds? You are in front a wall. You shape, bring down the damm thing, shape again. Bum!
  • You are firing. Them are firing back. You shape (natural armor again small bullets), charge, kill, shape again. The constant change from/to T.Rex at 2seconds each will be hard to pinpoint not matter what. The shock of burst to be so massive? Dude...

  • In front of you are (tanks\artillery\machine gun nest). You outrank them (by traditional means). Your position is excellent. You shape, get on top of it, destroy, shape, repeat.

  • The enemy is inside building. You shape, enter, destroy, shape, repeat.
  • You radar detect aircraft, you get into human. Hide. Continue.
  • You get that aircraft is problematic. You dispatch the team to be parachuted on top of (military base or anything that have that stupid planes). You jump, get into base, shape, destroy. Or jump as T.Rex with a full load of bombs, as a kamikaze, but you are not idiot so, shape again, the bombs fall and you get out skydriving. The defenses are nullified. Get into, do job
  • You inflitrate enemy country. Get into (HQ, Senate building, Presidential House). Afraid of be detected on door. You shape, charge ahead, bring walls down, get close to VIP, kill. Shape, disappear.
  • You are about to be captured. Good luck with that.
  • You decide to be captured. You get inside jail or whatever. You are about to be tortured... good luck with that
  • You are in the worst possible scenario. On open terrain, against a lot of tanks, you can't outrank them. Artillery shells are raining.

A simple T.Rex is done.


You are HUMAN. A elite soldier.

You bring T.Rex-Tanks (or: Armored T.Rex!) + T.Rex sized guns. to the battle. The enemy puny tanks.... And his crew are now complaining to the generals that totally were sure that a T.Rex is not useful on the battlefield...

You T.Rex can now become an mobile castle.


I think no, or at least mostly no. Early warfare involved a lot of up-close fighting but over time people have found ways to separate them from their targets more and more.

Even so, there is still some up-close fighting in certain limited settings, and this would be where T-Rexes might come in handy. For conventional fighting, their limitations would outweigh their benefits.

Ultimately, in combat between T-Rex and a guy with a gun separated by a meter or two, my money's on T-Rex. Put them 500m apart, and my money's on the guy with the gun.

  • 1
    $\begingroup$ @MonicaCellio: Thanks for the feedback. I appreciate constructive criticism and the opportunity to improve (entirely not sarcastic). $\endgroup$
    – Rissiepit
    Oct 31, 2017 at 4:54

Have fun ending holy wars when your elite troops are literally demons.

There are more drawbacks to shape shifting than the ability being good. On the bright side your elite troops will never be handicapped again. The can just shape shift from a one armed soldier to a two armed T-rex and then back to a two armed soldier.

Additionally, all that mass has to come from somewhere, so shape shifting would literally destroy the environment. Your elite troops would be pretty close to demons at that point. Every time they transformed the area would be engulfed in intense flame and matter around them would seemingly disappear as it was sucked into them. Going in reverse would be even worse. Matter would just be introduced back into the environment and the temperature change would be unbearable. To be honest, I'm not exactly sure which transformation would burn and which one would freeze, but that doesn't matter. It also doesn't matter what your soldiers transform into. The act of shape shifting would be the most effective weapon ever developed on any battle field. Transforming into something as stupid as giant earthworms would be bone chilling to witness.


No. They's be blasted. and they'd be useless in confined spaces, because if they tried to grow to their "t-Rex form" then, depending on the strength of the structure, they'd crush themselves.

  • 2
    $\begingroup$ Welcome to Worldbuilding! This reads a lot like a partial answer, so would you be able to edit your answer to include considerably more detail about how and why this is the case? Not every battle takes place inside a building and not everything that matters in a battle is the fighting either $\endgroup$ Oct 27, 2017 at 19:15

Yes, definately.

Play this one straight up, and armor that dino and equip him with laser assisted tracking miniguns. 3 Guns, a small one firing incendiary tracers mounted to his helmet, and two larger ones on the shoulder that are slaved to the head mounted one. Alternate armaments can be RPG racks. He armors up in camp, moves out with infantry. His battle armor can be easily made to resist small to medium arms fire. While he can deliver substantial firepower.

Think of it as rather than having a soft squishy tank, you have a heavily armed/armored 20 foot soldier, with the ability switch back into a normal infantry troop for retreat, or when the big targets become no longer desirable in the current theater. His battle armor could pack his standard infantry kit, it would just change into it when done with his dino duties.


Yes, with proper weaponry. They would not be carrying AK47's. They would be carrying cannons.

Edit: How the T-Rex would be carrying weapons is a mechanical detail (some sort of "carry on the back"? Put them down when shooting to avoid recoil?). The important point is that suddenly you have a battery of fairly-large cannons in an all-terrain vehicle.

  • $\begingroup$ So, would they be able to carry the weapons in their arms? How would the cannons have to be adapted for this? Why would that be a significant advantage on a modern battlefield? $\endgroup$
    – Secespitus
    Oct 30, 2017 at 21:15

T-Rex might be big and strong, but a M-16 bullet will rip into them just as easily as human flesh. It wouldn't be like the movies where the giant gorilla reacts to bullets like wasp stings.


  1. Speed (pursuit)
  2. Surprise attack after the human form was disarmed and captured
  3. Strength, to move or crush obstacles
  4. Teeth


  1. Limited use of equipment (although a vision of a t-rex with a bazooka is awesome!!)
  2. Transformation would have less armor and protection than human form in full combat gear
  3. Obvious targets (effectively automatic taunt)

Personally, it might be more flexible and have a greater story if each individual is able to transform into different animals. A scout might have an animal form that is quick and silent. A sniper might be able to transform ONLY his eye into an eagle's eye (and his entire body to travel quickly to new perch). Some may have roles to quickly move other team mmebrs and equipment in various terrains: water, land, etc. And then of course you have that one stupid hot-head (and life of the party) who transforms into that t-rex.


Honestly, I would rather have trained mosquitoes with diseases. They could fly in a week before and make the whole armed forces sick, and they are hard to stop. Bullets can't kill them. T-Rexs would not even make it in WWII against a tank brigade.


Well surely it would work if you're fighting against inferior soldiers with little military power, but if you're up against China or Russia, then forget about it!


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