For a story I'm writing I'm planning a large-scale battle between human mercenaries on the surface who will eventually come under attack by hostile alien forces. At first, the fight will feature small scale attacks from the enemy, who are attempting to force the human mercs to capitulate with minimal losses of their own. The humans have been hired to protect several tidal regions where their employer (another alien race) has eggs that are waiting to hatch and spawn, in much the same way frogs or fish reproduce. The eggs are valuable for several reasons, hence the reason for the contract.

But the humans are resource-poor and have few ships to use in the defense. As the battle escalates the enemy eventually moves in with ships of their own and secures the high ground, placing them in orbit above the surface.

Which brings me to this...how can the humans hold them off? The attackers won't want to resort to large scale bombardment and risk the valuable hatching areas, but that still leaves them with a big advantage. Once you control the air (or space), you control the battlefield.

What can I do to give my human mercs a fighting chance?

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    $\begingroup$ In what way(s) is the enemy attacking? Focused energy beam? Surgical bombardment? Air cover? Smart missiles? Ground troops? It's unreasonable to ask us to come up with answers to every possible way a ship in orbit can rain death down on their adversaries. Missiles could be sent from anywhere in the entire hemisphere of space. The question needs to be narrowed with additional details. What can the enemy do, specifically? $\endgroup$
    – JBH
    Commented Oct 19, 2020 at 2:22
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    $\begingroup$ Generally speaking, you want to wait a few days before selecting somebody as the answer. Many people don't read all the questions every day. $\endgroup$
    – puppetsock
    Commented Oct 19, 2020 at 20:41
  • $\begingroup$ Can you move eggs from tidal zone to other places and manually soak them as needed? If you can, you have tons of good options like moving to a cave system. $\endgroup$ Commented Oct 20, 2020 at 9:22

12 Answers 12


The humans need to buy time

In defensive warfare, this usually means operations that trade space for time. A game of traps.

There's a rich Jominian toolbox that the defenders can choose from, in the domains of space, air, and ground.

  • Diplomacy: Talk is cheap, particularly if negotiations go nowhere but buy the defenders a day or a week or a month. Encourage (through intermediaries) enemy politicians to question the expense and slow progress of their attack.

  • Outside observers: Maybe having nosy press and demonstrators around will delay the attackers as they pause to demonstrate that they are indeed obeying whatever rules that govern the conflict.

  • Deception: Make the attackers waste strength and time on shadows, rumors, and threats that never quite materialize. If the enemy hasn't previously surveyed the planet, then you can even deceive them on where the hatching grounds are.

  • Terrain, Obstacles and Obscurants: Orbiting baseballs, fog and smoke, nets and fougasses. Obstacles take time and effort to clear, they channel the enemy into your kill zones, they disrupt the synchronization of an attack. Enemy fighters show up without capital ship support (or the reverse); your ambush force inflicts heavy damage to the unsupported element, then scampers off to fight another day.

  • Spoiling attacks and raids: Make the enemy expend effort on force protection in their assembly areas. Every squadron on sentry duty is a squadron that's not pressing their attack.

  • Command and Control: Decentralize your forces, enabling local leaders to get inside the enemy's decision cycle, so your nimble forces can act faster than their chain of command can deploy an overwhelming response.

  • Economy of Force: Absolutely DON'T do frontal attacks or engage in a war of attrition (though you CAN feint such). Preserve your forces. Deceive, ambush, and trap smaller forces. Do not leave your dead and wounded and equipment behind. Every attack should have a withdrawal plan, and security for that organized and rehearsed withdrawal. Don't take unnecessary risks. Your goal is to waste time, not your lives.

Leadership and preparation is essential for the defenders. They will need secure communications, logistical support, and good intelligence on the attackers' goals, capabilities, and organization. And they will need time to prepare and conceal their redoubts, emplacements, caches, obstacles, observation posts, and ambush sites throughout the system.

In a perfect world, the defenders would be building strength (mass) for a counteroffensive. However, in this scenario, the best would be a stalemate...but the question seems to rule that out. So the defenders' goal should be to delay until 1) The attackers depart for their own reasons (hibernation season, change of politics, etc.) or 2) The siege is broken by an external entity (the employing aliens, the Galactic Patrol, etc), or 3) The eggs hatch and the objective loses it's immediate value to the attackers.

  • $\begingroup$ And now you have governmental military officials viewing your answer and taking notes to update and improve their emergency plans for alien invasions... Lots of good ideas here :D $\endgroup$
    – Davy M
    Commented Oct 19, 2020 at 17:02
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    $\begingroup$ @DavyM nothing new here for them. Jomini wrote all this two hundred years ago. Military schools have been teaching "operational art" applications of these concepts to company-grade and field-grade officers for generations. $\endgroup$
    – user535733
    Commented Oct 19, 2020 at 17:45

You hire humans because they are clever.

Both groups of aliens value the eggs. At this desperate point the humans make clear, to the chagrin of both their employers and attackers, that they do not give a rat's ass for the eggs and are ready to destroy them all before they fall into the hands of the attackers. In fact charges have been set to carry out exactly that. One such, at a small laying area, is demonstrated to make the message clear. A negotiator of the alien species who hired them is sent to relay this message.

The humans acknowledge that destroying all eggs will also bring about their own destruction as both groups of aliens will team up to slaughter them, and so they would prefer another way forward.

The humans offer a compromise. The attackers get 1/3 of the eggs. They do not get half because they are lucky to get any, but a representative from that group can choose the 1/3 that they take. The alien employers of the humans keep 2/3 of the eggs. The humans will accept 2/3 of their pay and safe passage off world.

  • $\begingroup$ and then the attackers come back again for more eggs, then what? $\endgroup$ Commented Oct 19, 2020 at 9:57
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    $\begingroup$ I think this idea could be improved with a minor modification-- change the destruction of the eggs to a percentage-based deadmans switch, or equivalent. Make it clear to the enemies that each merc that's captured or killed will destroy (1/NUMBER_OF_MERCS) percent of the eggs. If everybody is dead or captured, no eggs. Customer is happy because that would be the end result anyways, and the attacker is thwarted regardless. Unless the enemy wants to come try and grab the eggs while getting shot at, they have nothing left to gain by attacking, and should give up. $\endgroup$
    – Onyz
    Commented Oct 19, 2020 at 17:28
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    $\begingroup$ I don't really see any reason to give up or destroy any of the eggs. If the invaders are there because of the economic value of the eggs, then as long as the eggs are held hostage, the attack becomes profitless and they are better off just moving on to something they can make profit at. $\endgroup$
    – Nosajimiki
    Commented Oct 20, 2020 at 16:16

Pillboxes. The mercenaries are dug in in very tough pillboxes in the egg areas. Because of the eggs neither side can use any area of effect weapons unless the can completely confine the effect. At current tech level this means guns (and bows if someone really wanted to.) If a soldier can get right up to a pillbox they can toss a grenade in a slit, but that's all. Infantry vs pillboxes is suicide.

Note, also, that both sides are limited to carefully aimed single shots, there is no suppressive fire. Armored personnel carriers can help but they are of limited effectiveness as someone still has to get out to toss the grenade. This will basically become a sniper duel--with the defenders having a huge advantage.

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    $\begingroup$ I suppose you could surround a tidal zone with pill boxes (the ones on the ocean side being raised on pillars or some such). Problem is they are still 'fixed' defenses and once they have been spotted and mapped the enemy can 'Rod from God' or otherwise destroy them. And once they have blasted a gap in the circle at any point they have at least partial cover as they work their way around the along the edge of the defense ring. $\endgroup$
    – Mon
    Commented Oct 19, 2020 at 4:22
  • $\begingroup$ @Mon I'm not saying to surround, I'm saying to put the pillboxes in the area to be protected. You can't use rods from god on them because you'll destroy eggs. $\endgroup$ Commented Oct 19, 2020 at 22:46
  • $\begingroup$ Possibly but the rods are point impact weapons and the pillboxes are point targets. Yes, any miss will destroy eggs immediately adjacent to a hit - depending on unknowns like how densely placed the eggs are, how deep or even if they are buried and the depth of the sand/mud beneath the hit point etc. However if the hostile force has to come down and fight their way into the nesting grounds (in this case past pill boxes etc) then they are going to lose eggs anyway. Probably a lot more eggs and take potentially heavy casualties to boot. $\endgroup$
    – Mon
    Commented Oct 19, 2020 at 23:48
  • $\begingroup$ @Mon A rod from god is going to make a substantial boom when it hits, period. A direct hit throws bits of the pillbox all over the place and poses a danger to any egg in the vicinity. $\endgroup$ Commented Oct 21, 2020 at 1:43
  • $\begingroup$ Very true, though it also depends on the size/mass of the 'rod' the enemy chooses to launch and the velocity at which they choose to launch it. For the sake of the argument I'd assume that 'space navies' can select calibers (for want of better term) of the round they launch to match the target. But whatever they do, if the humans choose the fight the chances are that eggs are going to be destroyed. Attack from space - eggs are turned into omelettes. Land and attack from the ground - pretty much the same thing. Hence the suggested solution I added to my answer below. $\endgroup$
    – Mon
    Commented Oct 21, 2020 at 10:47

So. The goal is to capture a bunch of eggs and the mercs are trying to prevent that.

Using insane weapons is off limits as it can simply destroy the eggs.

Dropping an asteroid or using whatever continent destroyer ship-to-surface cannon you have is discouraged.

Thus the mercs need to continue protecting the egg until help arrives, right?

Because without the idea of outside help then the bigger force can simply play it like a medieval siege and chip away at the humans resources.

For example the attackers can simply destroy all organic life forms on the planet, they can burn the fields, poison the water...etc to force the defenders to surrenders. That's why I think the help arrives part is important. Because even a planet can still be badly damaged and lose it's ability to support life if you throw enough advanced technology at it.

  • The good old fortress. Imagine a fortress complex spanning the Himalayas mountains range, or just several kilometers. The complex has all the goodies of space operas: force fields, anti ship weaponry, stockpiles of weapons and other materials, factories and fields and all other stuff to create self sufficiency, and it can even be locked down to protect from CBRN attacks. Well. Those things are awesome to read about. Now if they hold up there then the thing might be to difficult to destroy or sneak into. If the shields hold then even missiles or cannons can't hurt it. Several meters of steal, or your futurists version of it, can further protect the things. Heck. The cannons may be able to damage or hurts ships in orbit. And of course tanks, aircrafts, and infantry is like a bunch of babies assaulting an elephant. Have them use one of those for obvious reasons. Now maybe the thing is old and crumpling, to create ore tension. Maybe it belongs to the original contract makers and they got the merc to man the place. Maybe it depends on a rare off world material that just happens to be so late so that they are on a time limit, seems lame but whatever. Heck. It might be too ancient and large that the merc are worried about being attacked from a place they did not know about. Maybe it is run by an AI. This can be a decoy. The eggs are in fact in an old watchtower with 1 guard while the fortress holds nothing. Whatever you like to modify the concept to fit your story
  • Needle in a haystack. The planet is home to giant, I mean absolute giant, forest or huge mountains or ancient mega cities or deep caves...etc Whatever it is it is like our thing but turned up to eleven. So the mercs are like: Well. Better keep the eggs in the heart of the super big forest with insane monster that can murder even power armored people. Same with other stuff. A mega city that covers an entire continent with vertical kilometers of structures some of which go back aeons. Good luck with that.
  • A submarine. Easy and simple. You can recreate whatever is needed for the eggs there.
  • Moving convoy. Even if they are big and need to be stable and protected. You can just create a special armored tank and put the egg there. No guns or crew, save a driver, and keep the eggs there. While the convoy is protected by helicopters, tanks, infantry...etc.
  • Off planet? Seems crazy. But can't they hide the eggs on the nearest moon base that is off the charts and sends no signals or even have visible energy emissions? Total darkness. With a small crew to protect it. The story can still be epic and all about how the attackers are doing this and that and in the end the eggs are off planet.
  • Trickery. Maybe you can arrange a deal with the mercs offering the eggs to the commander of the attackers. While they are on the ship they take over. Maybe they fly a bunch of transports really sneaky on the ship and the guys inside open the hanger bay. Like a space trojan horse operation.
  • Obviously if they have to cover more than one location without the numbers then they will need to have a highly mobile force. That high mobility makes it easier for the air-space holders to shut you down. That is why I ignored this particular aspect because it could be context dependent. I mean if you have to defend a city in Australia, a one in Turkey, and a one in the US. Without flying then this is really tricky. So I guess that you might feel the need to change something. Maybe they abandon an egg location. Maybe the mercs leave the civilians under the mercy of the attackers because they can't defend them. This is historical in the case of sieges. Maybe you want to change the importance of the locations. Maybe they do decide to destroy and egg or two because they are in undefendable locations.

You created a problem for yourself due to the requirement that the mercenaries protect several specific geographical points on the planet or fail in their mission.

Freed of that constraint the mercenaries might well be able to conduct a mobile guerrilla campaign/holding action by breaking up into small teams and dispersing so that they can't easily be hit by the ship's heavy weapons.

A key issue would be what you have equipped the soldiers with vs how good the enemies space based sensors were. You would need to give them very stealthy/low emission electronics and excellent camouflage equipment so they can hide, move and fight.

If they can't leave the egg beds alone then the only other option might be to entrench themselves right on top of the nesting grounds so that the only way the enemy can get to the humans without damaging the nesting grounds is to come down and dig them out in a fight.

Of course 'digging in' on a tidal mud flat presents its own unique problems???

AMENDMENT - a possible solution. Have the humans 'rig' the egg fields with high explosives or even tactical nuclear demolition charges on dead man' switches.

Then tell the attackers you've done it and that you'll fight long and hard to prevent the eggs being taken if the aliens press home an attack BUT the minute it looks the garrison can't hold you will destroy all the eggs. (You might even demonstrate your determination by televising the deliberate destruction of a small portion of one egg field for the attackers to see.)


  1. The aliens your contracted to can't complain because unless they're coming to the rescue (which in this scenario is not the case) they most likely going to lose all their eggs anyway.

  2. There's no upside for the attackers.

  3. From the humans perspective? Your not going to be paid if all the eggs are lost and even in the unlikely event you could win most of you will die.

  4. What the hell they're not your children (Cynical or what?).

(May as well put classic late 20th century terrorist tactics to some good use.)


Physically, there is no defense.

Consider that they have the recon in the form of observation from orbit. So they pretty much can see anything above the surface. So they know where you are.

Consider that a 1 kg iron bar coming in at 8 km/s (roughly low Earth orbit velocity) will have a kinetic energy roughly equivalent of 7.6 kg of TNT. Since the energy will be strongly directed straight down, you really can't effectively shield against it. And since that 8 km/s is round about mach 23, you get not much time to avoid. It's in the atmosphere for something like 10 seconds. It has the radar signature of a 1 kg iron bar. You'd be hard pressed to see that at 10 km with ordinary radar.

Such things are fairly easy to steer. You put tiny little directional vanes on the back, and it can home in on the exact coords you give it. They can probably put thirty in a row in the same hole with little difficulty. Fairly easy to get an error from one strike to the next of less than 1 meter.

The folks in orbit can pretty much kill off anything they want, with fairly surgical precision. Your ground vehicles. Your aircraft. Your pipelines. Your electrical connections. Your radio antenna. Your garden shed. Probably take the hood ornament off your classic car without puncturing the tires.

So physical defense is pretty much not going to work.

So the point is delay.

You might make some progress with psychological defense. Example: Where exactly are those eggs? Is that garden shed full of eggs? Is there a big container of eggs under that classic car? Is this airplane just taking off carrying many containers of eggs?

You could help that along by careful use of deliberately bad communications methods. For example, encrypted radio transmissions deliberately made to be de-encrypted. You could help the aliens believe in that by having an extremely easy to de-code version, then a mad scramble to tell everybody to stop using that one and start using the very slightly less easy to de-code version. Followed by a lot of self congratulation over fooling the aliens.

Then there are message with information saying the eggs are to be moved in stages in the convoys leaving on Tuesday, Wednesday, and Friday. Or messages saying that the local power reactor is dangerously unstable and any slightest damage could cause it to go and kill all the eggs, so get to work fixing it right now. That allows you to cover over a lot of construction and furious bringing-in and taking-out of lots of supplies and equipment.

So the exact location of the eggs becomes obscured.

You could fake a second batch of eggs for the aliens to capture and take. Say you give them 10,000 raw chicken eggs with green food coloring. And maybe infected with whatever is the alien equivalent of chicken pox. Decorate with radio messages cursing the guys who were supposed to be guarding the fake eggs. And a fake message to the client aliens apologizing for losing their eggs.

Or you could fake up yet another alien species coming to steal the eggs. This new species could, somehow, get by the original egg thieves, and the humans, and walk out with the entire inventory of eggs. They show up, do a huge CG-enhanced performance of stealing the eggs and going to their improvised staging area, where they set up a transmitter to call for their mother ship. All they really have is 10,000 raw chicken eggs with green food coloring. And their "transmitter" is a 1960s era TV broadcast tower.


Space Junk

Using ships or rockets deposit loads of space junk (rocks, metal) in orbit, making an protective asteroid belt around the planet. Will stop anyone coming in or out.

Set up defense near the eggs

Setup defensive strongholds next to eggs so any long range attack would risk destroying the eggs. Force them into close combat


As a last resort have C4 around all the nest. Warn attackers that if any invasion occurs you will blow the lot.

  • $\begingroup$ I came here to add the Space Junk option. Especially if you already have some satellites in orbit that you can sacrifice, just steer a bunch into each other and wait for the cascade of junk. $\endgroup$
    – bendl
    Commented Oct 20, 2020 at 14:05

Smoke, add systems that covers the whole area in a smoke that is inpenetrable to enemy sensors. This negates the advantage of space superiority scince the assets in space have no way to aim. After that it comes down to ground fighting where the defenders can prepare and have the advantage.


Using technology we have today might be enough.


We have ICBMs (InterContinental Ballistic Missile) that could be reprogrammed to become AS (Anti-Spacecraft) missiles. We also have conventional (non-nuclear) explosives that are more powerful than some atomic bombs. If you have fast enough missiles that can out maneuver defensive fire, this could be an effective method of attack. Launching more missiles than the attackers can track and defend against, overwhelming their systems would be another valid attack.


Nuclear missiles could also be useful, even if they don't make a direct hit. These explosions put off a massive EMP (ElectroMagnetic Pulse) that can fry systems within spacecraft. Sure, these spacecraft are designed to handle radiation from space and even fairly nearby suns, but a nuke going off just a couple of meters/yards off their hull is going to be many magnitudes more radiation and EM than that shielding can handle. Space doesn't have the medium for most shockwaves, but an explosion this big will create one for itself. This will likely tear through the hull and any shielding, so any subsequent detonations of nukes won't be shielded against, even if it isn't as close.

The problem with nukes is that at a high altitude, the EMP from the detonation could affect extremely large areas of the ground, too. I don't remember where I read it, but a single nuke detonated at the correct height and location above the USA could knock out the whole country's electronics, unless they were hardened, which most aren't. All consumer electronics, including vehicles, would be toast. Many commercial electronics (including electronics controlling manufacturing, hospitals, airports, and other industry sectors) would also be toast. The military would likely be fine, though.


We have a variety of aircraft even today that can fly so high, it's basically in space. These can be used as launch platforms to get missiles closer to the targets while maintaining good defensive maneuvering. This has the added benefit of surprise, for the first attack, anyway. Most weapons officers would likely realize the atmospheric nature of the aircraft, so write off their attacks as ineffectual. This is why it would only realistically work once, since the weapons officers, or their higher ranks, won't let that mistake happen a 2nd time.


Anything we have currently will only be made better in the future, as well as with alien enhancements to our tech and explosives. If the ground and air forces also have laser, plasma, or rail guns, these can be used as well, if nothing besides keeping the spacecraft busy while the missiles sneak up on them.

Since you have spacecraft to defend, then you can "dead launch" the missiles. This is where you launch them without activating the propellants until they are too close to be defended against. This is tricky, since you are shooting a "dumb" round at a moving target. If you can keep that target in the general area, such as by hemming them in with the ground based attacks, then you can activate the targeting and rockets on the missiles for a now short range attach.

Again, this may only work once. Any subsequent attack like this will be defended against. There may still be times when it works, but only as another "standard" attack with limited results, instead of something decisive.

A "dead launch" from a distance keeps your own craft safe from direct conflict with the attackers. This would help prevent your own attrition while hurting them. Once their weapons, defense, and propulsion systems take enough beating, you can unleash your undamaged ships and take significantly less damage than they inflict. These spacecraft can also be used to ferry/relocate supplies, materials, people, eggs, or whatever around the planet, so they are a critical part of your defense and shouldn't be used recklessly for an attack until it's reasonable the attack will be 100% effective to remove the threat from the planet.

Along with missiles, you can also dead launch magnetic mines that get attracted to the enemy hulls. These can either be detonated individually or they can be programmed to accumulate until there's enough in a specified area to do significant damage. A swarm of "tiny" mines is tougher to target and destroy than a single missile of the same explosive power. This is where the lack of a concussion in space helps, instead of hinders, you. Sure, there will still be fragments that could potentially cause a cascade effect, unless the mines are specifically designed/armored against it. These mines can also be made as shaped charges, so the armoring against fragments would double as the liner. The mines advance armor side toward the enemy, then affix armor side away from the hull. It's not completely foolproof, but would go a long way to making it difficult to defend against this type of attack.

Surface defense

Since the attackers have to carefully pick and choose their targets, you have the advantage. You can blow them up and not have to worry about much. Yes, some of the wreckage will head towards the planet, but significant portions won't. At least not right away. And significant portions of the debris will burn up as it descends, break up into small sections, and even slow down as it becomes smaller and hits more atmosphere. Large sections can be continually hammered with missiles and other weapons until it's small enough to not be a major problem. Yes, large amounts of damage will still happen, but there's only so much you can do to prevent it. If you don't completely destroy the attacking forces, they may decide to try attacking again. Hit them hard and fast enough and they should decide it's simply not worth it.


As other's have mentioned, diplomacy can possibly prevent attacks. Convince the attackers that an area is too important to them to risk a direct attack and they simply won't attack that area, unless it's being used as a military base or weapons supply depot.

Keeping communication open during the battles can also help. Once a section is badly damaged enough, they can offer to surrender themselves. This could be a ground base or a spaceship. Sometimes (maybe most times) it might be more important to save lives as POWs than to kill everyone.

Simply talking your way out of the war completely might not make for such a great book, though. But talking your way out of complete disaster can be useful to end a war before it becomes genocide.

Orbital systems

And of course, having orbital systems in place before the attackers even arrives is good. Having satellites that fire missiles, lasers, and all the rest can be the first line of defense. Even using a communications satellite to jam transmissions between spacecraft could be critical during a battle.


These Defenders Cannot Hold Territory

If the Invaders have uncontested control of air and space, the Defenders cannot hold any territory. Look to the recent combat against ISIS. Western forces were able to use imagery, air power, and local fighters to completely destroy ISIS, even though it had thousands of foreign fighters, and captured a country sized land area with several large cities to loot.

But They Can Defend the Eggs

Looking to other recent asymmetric campaigns, insurgents in Iraq and Afghanistan have killed and maimed significant numbers of Western troops over the last ~20 years, despite utterly lacking airpower, and having little in the way of real military equipment. The key difference, is that these insurgents understood they were in an asymmetric fight, and didn't try to engage superior forces in open combat.


The defenders create a network of concealed weapons, hidden communications methods, and cached food and water. They attack the Invaders at every stage of extraction: when the Invaders try to land, anti-air rockets. When the Invaders move to the Egg location, IEDs and direct fire. While collecting the Eggs, indirect fire (mortars).

Every time the Invaders try to engage, the Defenders disappear. Most Invaders raids end with multiple Invader casualties, no eggs - since the Defenders can afford to loose some, they destroy the ones the Invaders have collected to deny them that success - and they never even got a good look at their enemies.


The coastal location is interesting - the Defenders can supply themselves from inland using rivers. Rivers drain into the sea, and from the mouth of the river the Defenders can access the entire coastline.

Small boats and semi-submersibles could be the preferred method of moving equipment around, provided you can hide from Invader satellites. (If you can't handwave the satellite imagery away, you can use full-on submarines to hide from the eyes in the sky, but obviously the cost there is higher.)


An option would be to use the tried and tested shield method. The defenders have a shield which protects the eggs and the surrounding area. The shield cannot be breached from the outside however it can be passed through by low speed objects, like troops on the ground.

This would make ground assault the only option and taking down the shield generator a secondary objective to securing the eggs. It would split the responsibility of the defenders and add another high priority defensive objective to the mix.


Kind of a niche solution, but you can seriously threaten big spaceships with orbital debris if they don't have shielding or heavy armor.

Quick fact check, a head-on collision in low earth orbit would have a speed of around 15 Km/s, so a projectile of just 1 Kg would impact with 20 kilotons TNT equivalent of kinetic energy, which is in the ballpark of a WWII nuke. A Falcon Heavy rocket can carry around 60 tons to low earth orbit, so assuming you drop 1 kg projectiles ten meters apart in a square pattern, you can basically carpet bomb a 2 square kilometers wide region of space using a pile of bricks and a single 21st century rocket.

So, as long as you still have space-capable cargo ships or the technology to build them, you could threaten any ship that is parked in orbit, forcing them to either move in a random pattern and burn lots of fuel, without risking your own ship as it just has to get to orbit, drop its payload, and land. As stuff orbiting a planet usually goes fast, fast enough to go all the way from one side of the planet to another in a couple hours, you better have those sensors listening and engines warmed up if you're on the receiving end. And nobody says you can't drop repurposed railgun bolts coated with a stealthy material that prevents detection until it's too late.

As a bonus, this can also be a defensive measure if you know the enemy is coming way in advance. Just flood the orbital space with debris. Resources aren't scarce ? Instead of dropping bricks, drop guided, stealthy missiles that can be remote controlled to adjust their orbit so that they can "track" enemies or create opening for allies to pass through. Expensive, but less than a traditional planetary shield or a fleet of defense platforms. The cleanup will be expensive though.

  • $\begingroup$ The yield calculation is wrong. TNT yields 1.05 kcal/g, or 4.4 kJ/g, or 4.4 MJ/kg. 15 km/sec = 112 MJ/sec. So 1 kg of head-on LEO collision is the equivalent of 25 kg of TNT, not 20,000,000 kg of TNT. $\endgroup$
    – Jasper
    Commented Oct 16, 2023 at 6:40

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