An alien group attacks earth but fails, what level of military power they need to have to achieve that goal?

Question

I think the closest example is Nazi Germany attacking the USSR and Imperial Japan attacking the USA. Afaik the Japanese were not as suicidal as it appears, they had a particular goal in mind and it was all going to hell anyway.

And, again afaik, the USSR was not respected as much and the Red Army was though to be a push over by both the Axis and Allies.

Now this is not an attempt to talk about WWII, obviously, just some context to why it is possible to have such a scenario.

And so my story begins with an alien fleet that appears in our solar system on a sunny, ok it's meaningless is space but let me have it, Saturday and starts approaching earth fast.

A week later an alien "invasion" is launched

So what is the aliens thinking?

First of all they are a splinter group from their "state" they are radicals and believe in their superiority over everything. And they did arrive with technology the likes of which we can only dream of.

They also estimated that since humans are already divided into rivaling nations. It's much easier to launch separate attacks on each state opposed to what would happen if we had one single unified military like they do.

The military operation had specific and clear goals. So their initial target Are:

Military bases.

Human infrastructure.

Their ultimate goal of the attacks is not total annihilation but to weaken the collective human race enough so to bring them to the negotiation table so that a favorable agreement can be reached.

This agreement they want is just them getting lands to settle with absolute power over them and special statues among humans. Like they can't be trialed at our courts and so on. Which have a lot of historical bases.

I could not make them blind enough to believe they can destroy the human race.

Now they really want to destroy the military bases but when it comes to infrastructure they see the need for that later on, as they don't want to mess things up too much, so they won't focus on that heavily and won't utterly destroy them. Just enough attacks to cripple the country for a while.

Can't they just come in peace? No.

Why bother with earth in the first place? We are the only habitable planet they encountered, and having access to our own tech and infrastructure would actually give them a lot to work with. Because again they are not an arm of their state, they did not bring all the coolest toys with them from their own state. And so having a whole planet with more than 7 billion potential workers seems better than trying to settle in Mars.

They also see the subjugation of the humans as an important point in in validating their own believes and ideology.

What type of technology is available to them?

So far the most logical thing is a highly advanced ships with nearly unlimited power and large manufacturing capabilities. They have lot of drones and a crap ton of plasma and laser based weapons and vehicles. Most of which are controlled from their own ships by pilots or assisted computers, they don't have or like AIs.

The rest is up to you.

Their numbers can't be more than a few millions but that includes civilians so their actual military can't exceed half a million that if they put all capable males into it.

So when it comes to ground troops they don't have much. They use drones and their own tanks. Those tanks are obviously much stronger than ours but they can be taken out.

They don't actually have much of an air force, nor do they posses vastly powerful startship cannons. The air force can still be better than ours and still be decent. Their own ships are mostly armored and protected by shields for ship to ship attacks. But not top of the line invasion ships. This ties in with the fact they are a splinter group not the actual military arm of their race. So you if you want to add using their own ships for the attack do so but without making planet killer type of weapons.

Can they call support? Heck no.

Why focus on them? Because it's much easier to change the aliens than to introduce plasma tanks to humans with all the complexity that brings.

Do they have access to biological or chemical weapons or nukes? Initially they don't have them.

What is their military creed like? Mostly using overwhelming tech in the form of tanks and drones and so on to win the war.

So the focus is mostly on the type of vehicles they have and how to use them. But this would depend on the answer and I'm open to suggestions.

What is their biology like? Human like. Only more fragile and they detest manual labor and actually fighting.

Since they are space faring with vastly superior tech. I think they can turn the entire earth to glass if we wanted to, and thus the question and premise don't work! First they don't want to do that, second they actually have limitations. Also it's not fun.

Hopefully that's enough information.

This is getting long and so to sum it up they need to have a more advanced army, and initially do a lot of damage to our states but have their own "brilliant" plan fail within a time frame that I'm flexible to because it would depend on what you guy suggest.

And so I just want to focus on the answer to the main question and other points will have their own questions.

So. What is their overall military capability have to be in order to attack us but actually fail in achieving their goals?

Edit 1: to clarify the original idea is that they did not plan on our own invasion per se. They just escaped their own state and "happened" to find our little slice of heaven. So it would seem weird that they arrive with specific weapons or ideas to fight us.

Answer 1

Technology Required to Invade

Minimum

Engines

• Sufficiently high enough specific impulse to accelerate to a significant percentage of the speed of light (0.1c, 0.2c)
• Sufficiently high thrust that you could push accelerate a large load (thousands of tons) to cruise speed in a reasonable amount of time (around a year or two)

Power

• Anti-matter. At 0.3% mass-energy efficiency, as impressive as fusion power sounds, just doesn't cut it. You'll need $mass \times cruising speed^2$ energy to accelerate the fleet to cruise, and almost as much to slow back down. With anti-matter, a 20% speed-of-light cruise will require 8% of the fleet weight to be fuel (if the anti-matter power is 100% efficient); 16% fuel weight for a 50% efficient anti-matter plant.

Mechanical Engineering

• There are plenty of stars to launch an attack from within 10 light years of the sun. If cruising at 20% the speed of light, a 10 light-year trip will take 50 years (about; not including acceleration and deceleration) to arrive. The aliens need to build equipment robust enough to reliably start after half a century off.

Medicine

• Hibernation : the invaders will need to be able to put troops into an aestivation or hibernation that can be ended on arrival

Computing

• Autonomous Systems : the fleet will need to have semi-autonomous or autonomous systems with close to a human level of general intelligence to deal with all of the surprises a long space voyage could bring.

What Might Go Wrong

If the fleet takes a 10 light-year trip at 20% the speed of light, it will take about 50 years to arrive in the battle space. Additionally, light has a finite travel time (ten light years in this case). If an alien fleet arrives in 2020, invasion planners were looking at data from the 1960s when purchasing equipment and selecting targets.

In the 1960s, the Earth's population was 3 billion. Humanity had just gone through 2 back-to-back world wars (the 1920s and again in the 1950s) and we appeared on course for a third. Invasion planners might have assumed no (or very little) growth in the number of defenders and stagnant growth in technology (which still did not even include orbital space flight).

Based on the Alien Tech, and the Intelligence They Had Available, Here's an Order of Battle

(7) Missile Destroyers (40x 12 terajoule anti-matter missiles) : for use against military bases; one for each major belligerent during WW1 and WW2

(1) Aircraft Carrier (90x orbit-to-atmospheric small fighter craft) : only need one

(300) Troop Ships (10 thousand ground troops ea.) : - assuming 1,000-to-1 effectiveness of ground troops and 3 billion person population of Earth

Playing Through It

The fleet arrives in 2020. Where planners expected to arrive in orbit undetected, instead many observatories and satellites detected and tracked the fleet's approach.

Where planners had brought no orbit-to-orbit defenders (the fighter craft can fill the role, but were fitted for orbit-to-air and air-to-ground), there are now [26 countries with orbital launch capabilities]. Five of these nations have demonstrated nuclear weapons capability, and another four claim to have capabilities. 4

Rather than the uncontested landing of ground troops planners expected, the fleet encounters a primitive, but passable orbital defense. The alien ship engines are high-tech marvels for their efficiency, but under- or equally- perform chemical rockets.

And, completely unexpectedly due to the cold war, several nations have undisclosed, but supposedly enormous reserves of ground-to-orbit nuclear weapons.

Alien planning software has been active during the trip. It has observed with horror as peace has spread out over the Earth, and most of the plan assumptions are now invalid.

Nevertheless, the fleet commander attempts a contested orbital landing. The missile boats, carrier, and many troop carriers are destroyed during the battle.

The troops that do land find that the military bases that were valuable 60 years ago are now mostly closed. Tactical anti-matter warheads launching at pre-loaded targets detonate around abandoned facilities in the wilderness and desert.

The alien ground troops have to encounter larger ground and air forces than they expected, higher tech defenders, and most of their orbital support lost or wasted on worthless targets.

Answer 2

Most science fiction trivializes much of the space travel, but it would add lot of useful limitations if they did.

Space travel is tough. It should take a long time to get anywhere and even if you do have FTL there could be limitations that make carrying virtually unlimited weight in a ship impossible. So if you attack someone you bring three things: the people that you are going to invade with, a small amount of basic equipment to start the invasion and the manufacturingplants required to keep the war going after the initial engagements.

So the basic method of attack would be to enter the system. Land troops at some important points to secure resources and places to land your production facilities (or launch materials into orbit to the production facilities there). Then start a brutal war of attrition across the planet's surface in order to gain more and more control, hoping your production capacity and technology are adequate to win. "Real" militaries attacking similar tech civilizations would have access to space-based mining, refining and production facilities that remain in-system to produce everything needed while the defenders try to track them down and fight them before they have produced sufficient materials, but your splinter faction does not have access to those.

Your faction ends up not having enough people, resources and/or production facilities to win, either through miscalculation or successful attacks by Earth's indigenous forces.

Answer 3

Divide and conquer.

/First of all they are a splinter group from their "state" they are radicals and believe in their superiority over everything/

That is their leaders. Under those leaders are competent military persons. Within the first week of conflict it becomes clear from military decisions made who the competent military persons are. This is not a hive mind or a monolithic intelligence.

One of the reasonable military leaders is approached to parley. This competent military person has thrown his lot in with his radical leaders to escape his homeworld but his actions on the field have shown him to be less radical and more pragmatic. He sees how it is with the humans and realizes they have bit off more than they can chew. A land for peace proposition is made, with the condition that he be the new alien leader. He is no less arrogant than his leaders and sees personal and societal gain in the deal.

This reasonable leader turns and leads a military coup, with assistance from humans. Many aliens respect this leader and the coup does not take long. The radicals are overthrown and imprisoned. The humans keep their bargain and settle the aliens on earth under circumstances much more favorable to the humans. The humans also get all the alien tech.

Answer 4

They had fraction of C drives rather than FTL drives.

So when they surveiled Earth from their home a few hundred or so light years away, they saw a backwater bunch of apes barely capable of fighting off the most basic of plagues. Decades went by and technological advancement was minimal at best. Even being generous in estimating human development, the aliens figured we might be hitting the industrial revolution with a population of a few hundred million by the time the attack fleet/generation ships arrived.

Oops.

You don't need much to beat a bunch of states armed with muskets and maybe discovering a telegraph. That force might not be sufficiently equipped to deal with an order of magnitude more enemies, equipped with space-capable rockets, nuclear arms, and a high speed worldwide redundant communication system.

Answer 5

They Let Themselves Lose.

The only truly logical explanation is that the aliens secretly let themselves lose.

Any other extraterrestrial civilisation capable of interstellar spaceflight is likely to be millions of years, perhaps even billions of years, more advanced than us. To give you some perspective, it's the same as us going to war with some fish in someones backyard pond. Or actually, more like going to war with an amoeba in that pond.

So if you need them to lose, then it has to be their choice to lose. By why would they want to lose? I can think of many reasons:

• Because although our planet is nice, in reality, they have no real reason to win. Winning is not the real goal for the aliens.
• The war is a test. Not of us, but of themselves, to see if they could win with limited means. Kind of like us placing chemicals in the backyard pond to see if it will kill the amoeba, but we don't really mind if it doesn't work.
• They are curious how we would survive, to assess perhaps, or alter, our future trajectory of civilisation. Kind of like we are selectively breeding animals to make them more suitable for our use, entertainment or simple curiosity.
• A completely alien reason we cannot comprehend. I mean like 'because our scripture says so' or 'because it looks nice' or a reason we may indeed, never know.

To answer your question: So your technology level could be any level, and theirs too. To an alien, it matters not if you have guns or not, electronics or muscles. These are developments that have happened in a couple of hundred or thousand years: to them this period of development is a 'blink of an eye' in a billion-year timeframe such that it would almost seem instantaneous. Their 'military' technology level will always be beyond ours, far beyond anything we can comprehend now.

Answer 6

Sir, we have run out of bombs.

The plan is to simulteneously launch a bunch of tactical nukes or plazma/laser beans at all government buildings and military sites. This will leave most of the infrastructure intact while taking out the majority of world leaders and anyone who could pose an organised resistence. Then they move in an mop up.

Since this was the plan and space travel is expensive they only brought enough weapons for the first devastating attack. Then they were all out.

It usually works. After that show of force the planet capitulates. But humans are special because we were

(a) Too stupid to stop fighting. Sure the aliens can land their 25 hover tanks and mow down a bunch of civilians. They act all scared for a while and start doing what they're told. But the moment you move on they start acting up again.

(b) Too stupid to reorganise ourselves so the aliens actually had someone to negotiate with. Since there was no one in charge to negotiate with, the rest of the plan was a bust.

Answer 7

It is just about impossible for alien invaders to lose.

Interstellar travel requires control of vast amounts of energy. A spaceship capable of sufficient velocity change, or Delta V, to acclerate its mass to interstellar travel speed, should have sufficient Delta V to change the orbits of many asteroids and comets to fall toward Earth, and then to put those asteroids and comets in orbit around the Earth. When Earth has tens, hundreds, or thousands of asteroids in orbit, and the aliens can de orbit any one to hit any target on Earth, they can demand the total surrender of any group on Earth.

So it is just about impossible for aliens to fail to conquer Earth.

That is why all realistic stories about alien invasion end with alien victory.

So you will have to do a lot of thinking to come up with an poor alien conquest strategy that doesn't use their technological advantages well, leading to their failure to conquer, and then do a lot of thinking to come up with a psychological reason why the aliens choose such a poor conquest strategy.

Answer 8

It isn't their ship.

As several other posters have correctly pointed out, any civilization capable of building a fleet capable of reaching Sol must be so far ahead of us that we wouldn't even be children to them militarily. Taking out our satellites from orbit would cripple civilian communications and the economy, and pin point kinetic strikes would take out communications nexuses and military logistics points. If they can jam radio frequencies or decrypt our comms, the military's back to hard lines and PTP connections, both of which are short ranged (and PTP is line-of-sight), severely limiting our ability to call for help and coordinate troop and supply movements. We aren't capable of contesting their orbital superiority, either, so we literally cannot make any strategic progress. If they built they ship they arrived in, they can't lose.

So your invaders not only didn't build the ship, they barely understand how it works. Maybe it's an remnant of an ancient precursor civilization, maybe their species is a client of some much more advanced overlord, and this splinter somehow managed to seize an old, run down ship. It certainly could be a warship they just don't understand, or it could be a civilian craft; the tech is so advanced they can't tell the difference. So the ship could possess cannons that could destroy the planet or swat our satelites, aircraft, ships and bases, but the computers are locked down and the aliens haven't a hope of cracking them. Maybe the ship was built to be a local transport, and the FTL drive was a jury rigged piece of junk that broke beyond repair when the ship arrived in our system. Most of what they do use isn't used for it's intended purpose, with a corresponding loss of efficiency and increased component wear (which they can barely cope with). The ship has any number of ways to get all the power it needs just by sitting in orbit, but those systems are broken, locked down, or unknown to the invaders. Heck, maybe the main engines don't even work anymore, and they're putzing around with station-keeping drives that would take literally weeks to accelerate to respectable intrasteller (not a typo) speeds, and weeks more to slow down again. Not to mention, the aliens can't use the ship's tractors to nab a handy asteroid even if they had the thrust to tow it.

This puts your aliens in orbit around Earth and gives them advanced planetary-scale technology, but removes the reader's objections that any species capable of getting here is incapable of losing a war against humanity they don't intend to lose. They have to use what they have, and can't go back for more. Nor can they produce more, because even if the ship has that capacity, it's broken or locked down or other systems it relies on to gather raw material and/or power are broken or locked down.

Answer 9

IDOLIZE HUMANITY: You need a psychology that is sufficiently human to make their motives relatable, but sufficiently alien to defy conventional logic. Given the overwhelming practical advantages such a race would have over humans, there needs to be some flaw in the alien approach that leaves them vulnerable. Overconfidence and arrogance have been done a MILLION times, and is frankly easy and boring. They believe in their own superiority, yet detest fighting. They have a need to conquer humanity to satisfy their own self-worth and philosophy. They don't want to conquer the entire planet, but instead want to set themselves up in a place of privilege alongside the human race. Why do they want this? Because the think the Nazis were prophets, and idolize the human race.

• Their own culture long ago abandoned violence, but there are always those who look back on ancient practices with nostalgia. They found humans initially during WW2, and the information their probes sent back excited these folks about the "noble savages" on Earth.
• Traditions of cultural sensitivity shape their thinking, so conquering humans is merely being respectful of how humans interact.
• Given their admiration of humans, they will constantly overestimate what people will be able to do. Every defeat leads to panic and admiration.
• The goal is to make the humans admire and respect them in return. While collectively they are cowardly, individuals may perform great acts of courage; not to win battles, but respect of their enemies.
• Their emulation of the Nazis lends their behavior towards support of dictators and the establishment of authoritarian puppet governments. Right-wing revolutions would be supported, and liberal/leftist practices would bring attack and scorn. They might admire the Cuban authoritarianism, but then attack them because of their leftist ideology.
• In their desire for human attention and admiration, they will negotiate with world governments to try and extract respect and fear. If Egypt has a strongman who encourages them to invade Israel, they would respect the dictator and invade Israel. Getting the USA angry at themselves just proves they are worthy. A proper balancing act would be for them to flirty with a global war but always back down if they think they'll start too big a conflict.
• Play politics. So you conquered China with your fleet of drone tanks, now promise peace with Russia and trade with them. Don't invade North Korea - exterminate those Commie bastards. No use attacking Japan - you admire their militaristic history and don't want a full-scale war with the US.

Answer 10

So far the most logical thing is a highly advanced ships with nearly unlimited power and large manufacturing capabilities.

I dissagree. The reason why they are attacking Earth and wanting it's infrastructure intact is because they lack the manufacturing capabilities.

As you say,

First of all they are a splinter group from their "state" they are radicals and believe in their superiority over everything.

This could be explained by the splinter group stealing the warships. But those are warships, and they lack manufacturing capabilities. And they didn't have chance to take actual manufacturing ships, in which case they could just grab an asteroid an mine that. Also, due to the splinter group not being official, they might lack skilled officiers, commanders and soldiers.

So we have a situation:

Earth

• Populous
• Comparatively primitive weapons
• Fractured governments
• Manufacturing capability
• Want to defend themselves at all cost
• Despite fractured governments, many governments and militaries know and train to communicate and fight together

Alien invaders

• Few soldiers
• Lack of skilled officers and commanders
• Advanced weapons
• High ground
• No way to fix or create new weapons, including amunitions
• Don't want to destroy infrastructure

The first strike might go like Japan's attack on Pearl Harbor. The aliens will hope, that first attack will destroy enough military and break people's will to resist. But due to mistakes on commander's part and fast response of the governments, this attack is met with much heavier resistance. The war then turns into an attrition war.

Next assumption the aliens might have that the governments will not work together. Again, they are proven wrong when the governments of USA, China, Russia and EU all coordinate together at counterattack. This coutnerattack causes huge losses on both sides, but makes fast resolution of the war impossible.

Another assumption might be use of nukes. The aliens might assume the governments won't be willing to use nuclear weapons on their own lands. But once the humans realize the alien's technological supperiorty and the fact they desire the infastructure, they start using tactical nuclear strikes both to destroy the alien's weapons and to deny them the infrastructure they so much need.

In this scenario, technolgy doesn't much matter. Even if aliens can destroy 100 tanks, 1000 soldiers and dozens of jets for 1 of their drones, as long as Earth's infrastructure is intact, and the Earth governments are willing to enact Total War and Scorched Earth policies, they will loose the war of attrition.

Answer 11

Aliens secretly observed humans civilisation, than decided to choose different target. So conflict not started at all. And humans was too occupied on their own problems to find it

Aliens wanted to colonize Earth, because there is big oceans with clean water having good salinity level. Perfect for aliens to live in. Last time they send unmanned probes, humans civilization was just starting to build first railroads of 19th century. And aliens send few expeditions forces that will took ~ 200 years to get to Earth.

Alien expedition force used sophisticated cloaking devices and orbited Earth. Unfortunately, it was 2020 year. Aliens observed covid-19 quarantine in China, Great Toilet Paper shortage in USA, they tried to understand negative oil price panic (and their main artificial brain overheated), covid-19 quarantine in Europe and USA, Black Lives Matter protests in USA. Than they read human's wikipedia about first nuclear weapon usage to burn Hiroshima, while other civilizations they conquered used nuclear technology only for generating electricity or destroying asteroids threatening to wipe all planet's life. Also they watched some MBA broadcasts and live footage of military conflicts. Than they send few drones to find abnormal level of plastic in sea water of Earth, making it unusable for colonization.

Probably, if aliens was crazy enough as humans, they would try to deploy various biomechanic war machines like "Cthulhu" class heavy destroyers, "Godzilla" class medium destroyers, "Kaiju" class light destroyers, "Piranha" class anti personal systems and so on.

They even deployed few "Kaijy" scouts, but they died because one entered oil spill in Mexica gulf to suffocate to death, other one consumed too much plastic at Nemo point, and few ones were captured and butchered by Chinese fishermans... Aliens underestimated humans. And they asked themselves one question:

Why?

Why waste resources on capturing contaminated water and than trying to deal with natural born killers (who destroyed megafauna with sticks and stones in prehistoric time), that will probably survive on surface of planet after few orbital strikes and will start guerilla warfare or even send nuclear weapons powerfull enough to eliminate all live on their planet.

Also aliens found, that humans are predators, they like to eat burned meat of animals they killed and consume it, drinking methanol poisoned liquids.

It is something plankton eating aliens cannot understand...

Aliens did the math and decided human civilization is too crazy to mess with. They decided to leave humans killing their own keen and planet alongside.

Aliens moved to colonise Europe, one of Jupiter's satellites. At least it have clean water with funny leviathan grade fauna that can be domesticated, and humans civilization is too occupied with various strange things, so its unlikely they try to colonise Europe in foreseen future.

Answer 12

If I understand the question your asking correctly your concept involves a failed invasion i.e. aliens arrive and attempt an invasion but for whatever don't succeed fail. Humanity (or both sides) then have to set about dealing withe aftermath of that failure social, political and environmental etc.

If this is correct then the best possible scenario is one of numbers and logistics. Just getting here proves they have vastly superior technology but that in and of itself might not be enough. You also have to assume that for whatever reason the aliens want to preserve the environment as much a possible. Otherwise 6 aliens and a large asteroid would win the 'war' with one shot.

Consider a scenario where there was a say for example a steam age civilization on Mars. Could we currently send small teams of explorers there? Yes. Could we send a fully equipped expeditionary force to conquer the planet? No. You'd be talking about launching literally tens of thousands of tonnes of soldiers, equipment and supplies into space and then following up with tens of thousands of more tonnes for as long as it took for us to establish a large bridgehead and become more self sustaining. Even then you'd still have to send thousands of tonnes of stuff they couldn't source locally for decades. Even if we had the will we simply don't have the technology to sustain that kind of logistics chain.

The aliens have the same problem only they are hundreds or thousands of light years from home! No help is coming. So the most likely scenario is that they had to fight the war only with what they brought with them. And if they didn't win with that it means they weren't expecting to have a fight a war in the first place. So a refugee vessel escaping a war or a colony expedition stumbling across Earth is the most likely option.

Yes they have access to the solar system so presumably they could build/replace at least some weapons and equipment but what they cant do is replace their 'people' because they no more are coming for at least a couple of generations,if ever. This is especially true if you assume only a limited number of the aliens on board the ship were trained as soldiers to begin with or else could be spared to be used as such. So they end up having to learn the art of fighting humans as they go.

Even if the attrition rate was 10,000 to one more in their favor under this type of scenario the numbers are going to tell them they are on the losing end of the deal and its time for an armistice.

OK, so following your response -

The problem is that your question falls into the 'how long is a peace of string' category. There are simply to many unknown variables. e.g. How much more technically advanced than us are they and in what specific fields. What types of weapons did they bring with them and how many. Failing that what can they make/jury rig once they arrive. Same for soldiers, how many what type?

Remember as I said, technically even a very small team of aliens could de-orbit asteroids of any size needed for a specific purpose and drop in on our heads. No other weapon needed. Indeed That might be their 'go to' technique for taking out key targets and softening up an LZ.

But...when the ground/air fighting starts its hard to answer your question without some description of the forces at their disposal.

So in the absence of answers to that kind of question I think the best answer might be small numbers of control and tech types sent down to the surface to run localized units of war robots. (It's all very good to have a giant 'command center' in the sky) but at some point after you land you need eyes & brains on the ground. People who can make split second decisions at close quarters for your platoons and companies etc of robots in real time.

This might especially be the case because they won't/don't understand us at first contact i.e. we're 'alien' to them. Fighting their own kind? - no problem their robots can probably be at least partially trusted with a degree autonomy about tactical issues . Fighting us though? that means re-programming their actions on the run. And you cant do that if you don't see what works and doesn't in real time.

So I would suggest everything goes well for our alien friends until we start to figure out how they operate and concentrate on identifying their local ground based command teams and spotters/observers when we can find them. They may try to withdraw them eventually and run everything from space but that just slows down the robots overall co-ordination and the tide slowly shifts.

They do the calcs and decide - again that its time for an armistice.

The plus to this idea as I see it is room for lots of discussion around small unit tactics, spoofing and deception, booby traps and ambushes etc.

Answer 13

FTL is more or less the only tech they've got.

What?

Yes, that's right. They're generally no more advanced than us, but for whatever reason they do have technology to relatively easily and safely travel between the stars. Maybe they stumbled upon it by random chance (some alchemist smashed just the right kinds of rocks together in a mortar to get FTL dust - Earth doesn't have these exact rocks or simply never tried that combination), maybe some pieces of tech from another alien civ fell on their moon or even were given by these other aliens - as an experiment, or as a gift, or for the lols - nobody knows. Either way, now all they gotta do is make some neatly sealed boxes with some air/other life support in and they can zoom across the galaxies with impunity. Depending on how handwavy the tech is, they may barely need things like navigation or shielding, or it is all part of the tech.

Anyway, this is more or less how this plays out then:

One day, alien ship(s) show up on Earth. They very quickly erase any doubt about their hostile intent, land in the middle of big cities and open their gates to unleash the invading armies of terror. Only they're armed with bows, brittle, heavy gladii and maybe a crappy prototype musket or two. Best case scenario some WW2 level tech.

After the initial shock (aliens!!) the terrestrial military shows up and steamrolls the entire invading party, possibly captures most of them alive for questioning and study, and seize enough bits of their ships to reverse engineer and get some FTL of our own.

Now, I might be awfully specific here, mostly because it is actully the premise of a classic sci-fi short story by Harry Turtledove called "The Road Not Taken". There, the invaders have easy, cheap FTL, but this actually stunted their tech development so the best weaponry they have is a flintlock.

Answer 14

There isn't a believable one as long as it is a real war.

with the scenario you have laid out there is no reason the aliens over have tp put even a single one of their people in danger and they can can do any level of damage to us, up to and including extinction. They can easily force a surrender without a losing a single individual.

What is given

1. They have multiple ships with intersteller and intrasteller travel.

And that is all they need to win, they don't need anything else. they can drop rocks of any size they want, with bomb level precision, endlessly until we surrender. There is nothing on our planet they need they cannot get easier from asteroids including munitions. If they can make it here they have solved the closed loop food problem, and they have engines efficient enough to mine asteroids until the sun burns out.

Worse, they also have high end automation and a large population we are told this , meaning you cannot even rely on unexplained shortages, because again they can get resources and build anything they want without ever entering our gravity well.

weaponizing asteroids is just a question of math and propulsion both of which they have in abundance. To use your analogy this is Japan attacking the US, IF japans has hundreds of thousands of free ICBM's and we have not yet invented aircraft.

The only ways they can even put themselves at risk are to do several things that are breathtakingly stupid, which is possible, but not believable.

One possibility you have is it was not a real war to begin with basically the initial attack was done by a splinter/terrorist group and the aliens are actually peaceful and they make a show of surrender as an apology. There is nothing we can do to force a surrender and it would be a show not an actual surrender.

The only way we can win a war is if there was never a real war to begin with.

Answer 15

Their lack of AI would deny them a huge advantage, in that they would not be able to effect the (arguably) easiest form of invasion and seizing control. With an AI they would never need a ship to invade. Instead, all they would need is some bandwidth to transmit it over. But since they don't like AI, they wouldn't actually be able to successfully invade as I could see.

In a planetary invasion the natives are at an overwhelming advantage over any would-be invader, due to sheer number of people in militaries (let alone the hordes of shotgun-armed Texans.) To actually invade a planet like Earth successfully, they would almost definitely need an army of at least ten billion personnel. I highly doubt your fleet would have that many people.

Alternatively, they could destabilize the world's governments through insurgency. This would be (relatively) simple: use social media to make a population discontent, and then use this as a jumping board to incite rebellion on a global scale. Wait until insurgent groups have established global anarchy, then have your aliens come as saviors. Do a global COIN campaign, then rise to power through humanity's own political process.

Takeover complete.

Answer 16

They are not well-adapted to Earth

The aliens have higher technology, but earthlings are better adapted to the environment. Their home planet may have a lower gravity than ours (and the long journey on the low-gravity of a spaceship wouldn't help), our atmosphere may be toxic for your aliens, they may be susceptible to local bacteria and virii...

This can be worked around, but that gives humans an advantage. If they move slowly and need their space suits in working order, that makes light humans able to evade them, or even defeat them by damaging their suits.

You could imagine a cataphract knight battling against aztecs. The cataphract technolody (iron sword, horses, armour) is superior to actec technology, and just a few of them could decimate an army of actecs in battlefield. However, a knight is heavy, and requires supporting personnel (not available for your aliens). Enter on a forest, the aztecs could throw him from the horse (in which case he could barely stand up), prepare traps on the ground...

The best environment for the aliens is their own starship. However, placing it on a too-near orbit would risk it being damaged by Earth missiles (space is a bad place to be with a damaged ship and, if the invasion failed, they need their ship to safely go somewhere else), so they have it on a quasi-random route, only getting slightly nearer when sending/receiving a ship. On the other side, Earth would probably have automatic missiles "patrolling" the higher layers of the atmosphere, programmed to hit any object larger than X.

Also, trips to the ground (alien tanks, provisions, more soldiers...) are highly vulnerable while descending. There are only some angles suitable for re-entry, and there is a lot of kinetic energy to lose before landing. Yet, an ship-sized object entering the atmosphere is easily detectable. Re-entry becomes much more complicated if you additionally need to dodge the enemy bombs!

Answer 17

It seems your after a military capability 'number', that's high enough to justify starting the war but low enough for loosing. Warfare has so many unknowns and huge mental components that other answers discuses in detail. It is misjudging morale, political will, tactical skill, ruses, sabotage, second/third/fourth order effects on actions that make it hard to judge military ability. It entirely possible to misjudge combat ability that isn't revealed until the war starts.

So. What is their overall military capability have to be in order to attack us but actually fail in achieving their goals?

I think all they need a low risk option they believe will be available no matter what. Like ability to strike from space, without interference. So long as they can hit big targets without risk, you would assume they always had a fall back tactic.

All drone based invasion is a risk, even if they are all destroyed, you can still have your space battleship bombing cities you can always retreat.

They knew all along they may never win total victory (because they are sound tacticians who understand they lacked details about earth), that maybe they had to settle a deal after constant orbital bombardment, but they could have ALWAYS retreated and moved on if needed. How is this not worth rolling the dice on?

*I think its also false to assume settling a preferential peace deal means a loss, and not a victory.

Answer 18

Whatever tech they have, they should have very serious issues with it

If a fighting force is capable of interstellar travel, them failing achieving military goals (against militaries of Earth) does not sound credible at all. That is unless something is seriously wrong.

The possibilities could be:

• alien force is in a very bad shape at the point of arrival. This may be beacuse they had to fight their way out of their home state and now most of their equipment is severly damaged/unusable
• alien force is not a fighting force per se. They are paramilitaries mostly armed with small arms and no (or very limited) access to heavy equipment. Or maybe they are not militarised at all - their flet could be a resource extraction and colonisation fleet, not equiped to fight at all and all weapons they possess are converted from some civilian tools and vehicles

It sounds to me that whatever option you go for, in order to botch the invasion, aliens must be unable to maintain air(and space) superriority. Given that - Earth militaries have a chance.

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ANY tech + Inability to capitalise on initial success

If you want aliens to to be proper fighters with tons of hardware, the only scenario I can suggest is the initial success of milatry campain but a subsequent failure of occupation for reasons unrelated to pure military might. Aliens may have miscalculated in evaluation of their supply chain and are unable to establish/maintain/protect their manufacturing facilities on Earth. This coincides with lack of manpower to succesfully maintain occupation and eventually they are forced to negotiate..

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Lust for battle

Lastly, it sounds like your aliens should be very bloodthirsty to proceed with the invasion. Your stated goal of getting a chucnk of space for themselves could be achived through alternative means:

• coercion: "give us this, or we will drop an asteroid on you"
• trade: they may establish a corporation manufacturing consumer goods using their secret tech and be quite successful in embedding themselves into global economy, using the profits for establishing gated communities in paradise-like spots for alien elites
• cooperation: they can help solve some of our issues related to arable land, turning deserts into farmaland and forsets keeping a small areas for themselves as a 'fee'

Why wouldn't they want to do any of the above? The answer should provide an irrational reason - religion/tradition/etc.

Answer 19

The only way this type of force could conceivably fail would be failure of political will. They may have assumed that they could win by killing a few million humans (which they can do with impunity, being able to strike from way beyond the reach of our weapons); then they find that they have to kills tens or hundreds of millions. The slaughter is eventually too much even for them. What are their news media like?

Or, if you want to go the allegorical route, they easily defeat the Earth's combined militaries, but then have prolonged actions by human terrorists chipping away at them and their human proxies. The humans only kill a few aliens a year, and millions of humans are killed, but again the aliens political will fails and they get fed up with this interminable, unwinnable war. They eventually pull out of Iraq/Afghanistan/Earth.

Answer 20

Another possibility: They don't actually have their tech. Your aliens original purpose wasn't invading Earth. Rather, this is an enemy warship that is seriously damaged by some means. It expends the last of it's maneuvering capability to attain solar capture at something like Earth's orbit. All that's left are strike craft with energy weapons and shuttlecraft, both of which don't have much more life support range than needed to reach Earth during a conjunction. Their objective is to make us submit to supply what they need to fix their ship, but they are set up for space warfare, not invasion. They can do damage while the conjunction lasts but then have to wait years for the next one, when they come back they get a very hot reception.

Answer 21

Their strategy relies on alliances. Which fall apart.

Like you say, they find an Earth that is fractious. So they identify terrestrial powers that have a big enough military to succeed with support, and a government that is either

• unprincipled and opportunistic enough to ally with the aliens for their own world domination (Saddam, or perhaps the Russians), or
• ideologically principled in a way the aliens claim to be aligned with (China, EU, US).

This then fractures, because the aliens don’t plan to keep their promises of power sharing, and/or turn out to be not so well aligned with values after all.

Their ally figures this out, possibly because the other nations convince them of this diplomatically.

They then do a heel-face turn, taking advantage of their integration with alien forces to “catch them completely off-guard”.

Partly for cultural reasons, the aliens do not see this coming.

Answer 22

Why bother with earth in the first place?

War is messy, and even if you win, some of your ships might be damaged beyond repair.

they detest manual labor and actually fighting.

If they detest manual labor and fighting, why in God's name are they fighting instead of negotiating? "You give us what we want, and we'll give you what you want."