Is it realistic that an advanced species isn't good at war?

A non-human society is engineering minded by nature and is extremely advanced, to the point where they (with wide-scale community effort) have learned how to create wormholes and have practical space travel.

Is it reasonable that they are simply clueless on waging war? I want these people to have sought out humans to help them win a war against another advanced species, but it seems like any technological society would be able to figure out how to fight and destroy.

To be clear: they're not looking to Earth for advanced military technology, but rather military strategy. Is it plausible that they haven't figured out how to mass produce weapons, arm and train soldiers, manage and attack supply lines, develop countermeasures to enemy technology, spy on and decrypt enemy communication, and generally dream up more efficient ways of defeating their foes?

• This reminds me of Larry Niven's Puppeteers. Manipulative cowards who use other species for anything dangerous like exploring (or war). – Henry Taylor Oct 3 '19 at 18:37
• Look up the Kzinti Lesson from Larry Nivens book "The Warriors". – TheDyingOfLight Oct 3 '19 at 19:56
• This is exactly the storyline of the Damned trilogy by Alan Dean Foster. en.wikipedia.org/wiki/The_Damned_Trilogy – Thorne Oct 4 '19 at 6:27
• See Galaxy Quest imdb.com/title/tt0177789 – FunkTheMonk Oct 4 '19 at 8:50
• Maxim 24: Any sufficiently advanced technology is indistinguishable from a big gun. – Mason Wheeler Oct 4 '19 at 19:58

Sure. It's even possible to be very familiar with violence and not be good at warfare; think about the difference between a warrior and a soldier (current US military propaganda notwithstanding): a warrior is an individual. A soldier, by definition, is one element of a fighting group. Being good at one doesn't automatically mean being any good at the other. You could imagine a species where singular dominance battles are common yet the idea of ganging up in an organized fashion beyond temporary and immediate groupings of convenience never took hold.

And it starts at the basics: modern military training and indoctrination is the result of decades and even centuries of hard-earned experience in what works and what doesn't, and it's always evolving and being refined to take into account cultural, societal, and technological changes. It's not something that can be avoided.

A good example is the American Revolution. Historical myths to the contrary, it wasn't a bunch of freedom-loving non-military farmers who took up arms and defeated the British Forces out of pure patriotism and the power of liberty; just about all the British military defeats relied on the colonists eventually fielding trained forces. Even Lexington and Concord. Historical research has shown that a great many of the colonists were in fact veterans of the French and Indian (or Seven Years) War, and thus trained troops; if anything it was the British at that fight who were inexperienced, many not having previously been in a conflict. But on a larger scale, the Americans spent much of the early part of the war in constant retreat until they'd accumulated a cadre of battle-experienced troops and imposed traditional European-style discipline and training so they could have a chance in open battle.

Which Washington, incidentally, was well aware of; an experienced soldier himself, he had a low opinion of amateur militias based on his own experience. The army that took to the field at Yorktown was a professional, conventional one. And the same lesson had to be learned in 1812. And 1861. At least by 1917 they figured out you couldn't throw untrained troops into the meatgrinder of modern warfare and expect them to survive with only the love of liberty protecting them. Turns out that isn't very bulletproof.

Not that this is a uniquely American thing; the Russian communists had to figure out the same lesson. It took Trotsky reorganizing (well, creating, essentially) the Red Army, employing experienced former Czarist officers and non-coms to train the troops, before it became really effective on the battlefield, having realized revolutionary zeal didn't overcome aimed firepower and professional military tactics.

You'll note in those two example technology wasn't the important factor. In both cases the two sides had at least equivalent weapons. Both sides had literate leadership capable of reading and knowing the theory of successful warfare based on history and the experience of others, but it took until they had troops drilling on the parade ground with sergeants bellowing at them, mattresses being tossed in the barracks for not having the corners done correctly, and people doing pushups until they puked until they got it into their heads why you only pointed the weapons downrange that they could get on the battlefield and be expected to win and not have to rely on luck or the enemy screwing up.

Relevant to your question, in both cases these are human groups, in real life who had to learn that lesson, and you still see it happening today. People who think that because they've got a military weapon they can take on a military force. Give me a bunch of yahoo "militiamen" and a company of Marines (US, Royal doesn't matter) or from just about any other professional military with the same weapons but half the size, and they'll cut through the "militia" like a hot knife through butter the vast majority of the time except in very specific circumstances. And again, these are people who have access to lots of history and documentation demonstrating over and over why some things work and some don't, and yet that information simply isn't incorporated, despite example after example why it has to be.

So that being the case with humans in reality, it's hard to argue that aliens in fiction couldn't have that same sort of problem. The difference being, in the case proposed, the aliens are smart enough to realize they have the problem.

There's another factor that could come into play. Humans seem to have an inherent hierarchical instinct where people will naturally form groups and will tend to follow those in a leadership position, however that leadership is recognized as legitimate, whether through the leader imposing their will and control, or whether the group chooses the leader, or anywhere in between. That makes organized conflict something also inherent and natural; note that the most popular sports tend to be team sports, and what are team sports but organized, controlled, conflict between groups operating in a unified, cooperative manner? It's such a part of us that even our recreational and play activities exhibit it.

Another intelligent species might not have that instinctive "feel" for that sort of behaviour. They might have evolved as more solitary creatures, and recognize intellectually the benefits of cooperation, enough that they've built a civilization, but don't have the instinct to cooperate and follow orders from a leader that humans have. That's going to have repercussions, especially if you combine that with sketchy knowledge of military training. In stressful situations, most people will look to someone to be in charge of the situation and will follow instructions, an instinct military indoctrination reinforces. In a species without that instinct, someone given orders might stop all the time and consider if that's the best thing for them to do, which in a battlefield can get you or other people killed.

• "yet the idea of ganging up in an organized fashion beyond temporary and immediate groupings of convenience never took hold" That would be an artificial blind spot though. A civilization is defined by doing things together, and it's done because it's beneficial doing things together compared to doing it alone. I don't see a reason why a species that understands this principle and applies it to other facets of their life somehow would never apply it to violence. – Flater Oct 4 '19 at 10:49
• If individuals don’t cooperate for personal security advantage, are they really likely to cooperate in all manner of ways that would be required to achieve the technological advantage described in the question? – eggyal Oct 4 '19 at 11:36
• ...I’d suggest that’s only likely if resources are so plentiful that there’s never any tension over their use/control. – eggyal Oct 4 '19 at 11:45
• I would also add that scientific knowledge doesn't just give you military technology for free. The level of scientific knowledge required for a machine gun is actually no higher than for a blunderbuss, but the two were hundreds of years apart (this might be more engineering than know-how though). If a complete lack of warfare is taken as a given it is completely plausible that space-faring aliens first attempts at making weapons would be worse than modern human stuff despite a massive difference in scientific knowledge. – Dast Oct 4 '19 at 13:44
• @Dast, I think a bigger issue would be between developing a weapon and developing a practical weapon. Again, you can see the same sort of thing happen in real life where there are lots of ideas for really cool weapons systems that would be awesome in theory but fail utterly in practice: flying tanks; pycrete aircraft carriers; Project Thor. All of them sound great until you get into the practical issues, and sometimes those practical issues aren't obvious unless you've got the background to realize that. – Keith Morrison Oct 4 '19 at 16:39

They evolved with "Us against the Environment" (which requires cooperation and technology), not "Us against Them" (which requires warfare)

Evolution of intelligence (and hence technological advancement)

Many theories of the evolution of intelligence (in humans and animals) rely on a machiavellian drive. For example if a species has complex social interactions (e.g. chimpanzees) they need to learn who's who, who's dominant, changes in dominance hierarchy, how to deceive others to obtain food, getting and maintaining allies, forming "war" parties to fight other rivel groups etc. But there are other ways we can see intelligence developing - like extractive foraging (you need tools and techniques to get food - see New Caledonian Crows) or omnivory (learning what is safe to eat and where to find it - see rats) or pair bonding/social group dynamics (and the complex social interactions that result from that - see parrots and elephants). In fact when we think of animals that most scientists consider intelligent many are relatively peaceful and pro-social, like parrots, elephants, whales, rats, octopuses. Even among great apes, orangutans, gorrilas, and bonobos are relatively conflict free (besides fighting over mates/territory). So we can evolve intelligence without the need for self-serving conflict but is conflict the inevitable result of society?

Society without war?

Most conflict is about resources (food, shelter, mates etc). One could argue that conflict can also be about ideals/culture (holy wars, genocide etc) but even those conflicts are probably underpinned by the perceived threat of resource shortage. If there are enough resources its just not worth your time, effort, or risk of injury to fight. So is it possible to have a society without inevitable resource shortage? What about an environment that is so risky, populations never get big enough to have resource shortage and conflict - e.g. poison gasses frequently spill from underground in unpredictable places killing large parts of the population off; some type of radiation or something from space; a rapidly evolving pathogen that the society (despite their technology) has not been able to purge but keeps baseline population low. These challenges you cant fight with war but with technology and cooperation. Once the species becomes space-faring they may no longer have to deal with the environmental threat but at this point they are having fewer offspring (like many nations today) and have more resources from other planets. Or perhaps that pathogen has followed them.

• +1 for avoiding the assumption of others that evolution on some unknown planet necessarily exactly the same constraints and influence as it did here. – WGroleau Oct 4 '19 at 15:19
• Humans will be technically just another "environment" to them. They'll be good at war. Maybe they will not call it "war", but they'll be good at it. – Oleg V. Volkov Oct 4 '19 at 16:47
• @OlegV.Volkov Environmental adaptation and science itself is all about understanding cause and effect. Tactics are all about deceiving your enemy into responding the way you want them to. The human concept of tactics would violate these alien's very basis of logic to the point our tactics would seem like a magical psychic power to them. They intercept a message that their outpost will be attacked by 5 ships, they send 10 to reinforce, we show up with 30. Next time they assume we will send 6x as many ships as we say and we just attack somewhere else. Humans make no sense. – Nosajimiki - Reinstate Monica Oct 7 '19 at 21:01

Clueless? No.

Even herbivores are deadly when threatened. The law of nature is a dog-eat-dog world, without that kind of pressure, evolution is impossible. At best, a species may be able to get away with hiding, but once a species develop intelligence, they start requiring things which can't be hidden, like smoke from fire. Pacifism is a luxury of those with weapons or defenses.

However, it's very possible that they'd be able to form a society without the level of fighting that humans have done if their psychology is distributed more towards a defensive culture and a strong mental block against fighting. The thing about combat is that a small group willing to fight can causes everyone else to respond in kind, or be conquered, so they would have to make defenses - but offensive strategy may be mostly unknown to them.

That being the case, they'd have no experience with offensive combat - compared to humans, which their observations would reveal that large swaths of the population are constantly engaged in mock war-games with each other. And they've even programmed futuristic military simulations, the primary one called 'Starcraft II'. Humans sound like a great choice.

• It's worth adding to this answer, that while just about every animal fights, that is very different from war. There are not that many species where groups fight each other for dominance, even though individual fights for dominance are common. The counter-counter point is that any species which has reached the stars must be communal, which is the subset of species where something like war can occur. – Turksarama Oct 4 '19 at 4:47
• “The law of nature is a dog-eat-dog world, without that kind of pressure, evolution is impossible.” Evolution tends to lead to competition, not necessarily conflict. And even if, maybe they’ve wiped out all animals on their planet long ago? – Michael Oct 5 '19 at 8:43
• Even herbivores are deadly when threatened. While this may be true of many/most herbavores, there are some herbavores for which this is absolutely false. Some examples come to mind: the fainting goat, the Galápagos tortoise, and the dodo. – cowlinator Nov 2 '19 at 0:28

The supercolony.

Consider the Argentine ant. In its native lands, different ant colonies fight each other. But in the course of invading new lands, this ant has formed a supercolony. It is something different.

https://en.wikipedia.org/wiki/Argentine_ant

According to research published in Insectes Sociaux in 2009, it was discovered that ants from three Argentine ant supercolonies in America, Europe, and Japan, that were previously thought to be separate, were in fact most likely to be genetically related. The three colonies in question were one in Europe, stretching 6,000 km (3,700 mi) along the Mediterranean coast, the "Californian large" colony, stretching 900 km (560 mi) along the coast of California, and a third on the west coast of Japan.

Based on a similarity in the chemical profile of hydrocarbons on the cuticles of the ants from each colony, and on the ants' non-aggressive and grooming behaviour when interacting, compared to their behaviour when mixing with ants from other super-colonies from the coast of Catalonia in Spain and from Kobe in Japan, researchers concluded that the three colonies studied actually represented a single global super-colony.

The researchers stated that "enormous extent of this population is paralleled only by human society", and had probably been spread and maintained by human travel.

Ants from the supercolony will not fight each other. Any part of the supercolony is as good as any other part. The ants can be aggressive against food sources and defending the nest against predators. But "war" means organized aggression against conspecifics and these ants have dispensed with war. In doing so they are on their way to conquering the ant world. In Southern California, it is hard to find any other ants but these.

So too your aliens. Through cooperation they have conquered their world. They have no experience making war on an intelligent adversary.

Humans: be very careful what you teach these creatures.

• That's a simple colony based creature. The engineering skills are genetic, and unless this super huge colony is built structurally differently than the ant colonies are built in Argentina (there's no indication of this) it appears that those ants don't show any progress (progress of skills). OP is proposing a world where technology progressed, and I don't see technology progression here - just a larger home. – J. Chris Compton Oct 4 '19 at 14:14
• @J.ChrisCompton Unless you're suggesting that gaining technology will make the ants more likely to wage war against themselves, I don't see how that plays into it. Its at least plausible that a species that doesn't wage war before it dominates a planet would retain the same trait after evolving intelligence and technology. – mbrig Oct 4 '19 at 19:10
• @mbrig As stated in the quote, the ants "had probably been spread and maintained by human travel." This is a great analogy if OP was asking about aliens taking multiple races from Earth and dropping a mixture of them on lots of different habitable planets and finding later that in some cases, there was no war on those planets. But OP seems to be asking about a non-human society advancing by itself (without influence). Without humans influence Argentine ants would still be at war everywhere they exist. – J. Chris Compton Oct 4 '19 at 21:45
• @J. Chris Compton: humans are not responsible for the fact these mutant ants cooperate. That is something particular to the ants. Humans are responsible for allowing the colony to get established in Japan and Europe where the ants could not get on their own. In California they are spreading just fine without help. – Willk Oct 5 '19 at 22:06

Imagine a society with generations of pacifism. They have no generals. They have no weapons or battleships. They might understand the concepts of waging war, but it will still take many many years for them to train generals, or build the infrastructure necessary to create weapons of war.

How long do you think it takes to train a general?

How long do you think it takes to create the infrastructure necessary to construct a battleship?

Your non-human society is going to be looking for those with experience. It's unlikely that they've never seen violence (think about the conflicts in the natural world), or they haven't read stories and tales about battle (think fiction), but they need the expertise of humans who have lived through these conflicts before.

• For a good reference on this I suggest everyone to read or watch Seven Years in Tibet. – Renan Oct 3 '19 at 19:07
• Also read Dilbert. In one strip, Dogbert hopes that everybody on the planet will become pacifist. That way he can take over the whole place with just a butter knife. – puppetsock Oct 3 '19 at 20:08

If they have advanced spacefaring technology long before they encountered another intelligent species, they may have almost completely conditioned themselves against war and war like thinking. To make it more believable perhaps they have engaged in large scale gene editing to make violence very difficult. possibly something like super-empathy. Above a certain level of technology going to war with your own species basically means the extinction of your species. Works even better if there is more than one habitable planet in their system so their ancestors had to make a choice about altering their behavior or going extinct through interplanetary conflict. It helps if they had a close call in their history, a terrorist cuban missile crisis with FTL technology (to stretch a analogy), something that made the realize one lunatic could wipe out their entire species.

Hundreds of years (now) later they can reinsert/remove the genes but they have lost all knowledge in how to socialize these violent children, so they keep ending up with hyper-aggressive lunatics that are far more dangerous than the enemy. So they need a species that is still knows how to socialize potentially violent people.

• Take it a step further and a civilization colonizes several planets with these modified beings with the intent of using them as slave labor, but they end up wiped out (for whatever reason) leaving behind these pacifist colonies. – rtaft Oct 4 '19 at 16:54
• Wouldn't that empathy only work inside their own race? So they'd be perfectly fine with warring with outsiders? Or if they're that powerful that they can push into another race's mind, wouldn't they pacify humans instead? – Oleg V. Volkov Oct 4 '19 at 22:22

You don't neccessarily need them to be completly void of war in their history for them to be really bad at modern war.

They may have fought wars in their past, but that was 4000 years ago when they were in the technological equivalent of roman or maybe renaissance technology. And due to (poltical development/religion/different evolutionary psychology, etc.) they managed to not have wars since.

So now that war has come to them they are kind of helpless and don't know how to deal with the situation. They managed to design some pretty good plasma rifles and they got a million of them rolling of the assembly lines every day - after all that is just a bit of high-energy physics, metallurgy, mechanical engineering and mass production - things they are doing everyday anyways, but military theory takes time and experimantation and iteration and that's something they don't have. So they could try to figure things out on their own and suffer horrible losses in the meantime, or they could just ask the humans and we give them general staffs, military ranks, combined arms, medical and engineering corps, division, and all the other nice stuff it took decades or centuries to figure out immediately.

For the sake of variety I will pursue an argument about game-theory and not biology/psychology.

From an engineering standpoint it would have a very odd advanced civilisation to not be able to apply economies of scale and logistics to prepare properly for warfare.

That being said I think it is indeed plausible to lack experience in actual wartime strategy and economy. Eg. their societal history must not have encountered any scenario where game-theory or optimisation has ever been required. So either this civilisation has negligible conflict history or their weapons technology was so advanced that they completely steamrolled/blitzkreiged every enemy they have ever fought. Perhaps the setting can be a situation where their previously effective weapons have been completely nullified.

Human wartime history is a repeating tale of new paradigm/technology shifts that make old doctrine obsolete.

• Wartime Industries: see German complexity vs the American Warmachine of WW2, where streamlining manufacturing and material consumption was a distinctly acquired skill for prolonged conflicts with a need to rearm/raise additional troops.
• Professional Soldiers: The transition from Levy to Professional standing Armies was a distinct reaction to improved agricultural efficiency and an outright need for permanent as opposed to seasonal troops.
• Logistics: Campaign complexity and length is directly proportional to the sophistication required for ensure safe supply logistics.
• Spycraft/Encryption: Battle plans/strategy needs complexity to justify spycraft value. Eg. Ancient combat spycraft was limited to choosing the location of battle and troop formation.
• Combat Tactics: There needs to be a prolonged conflict for any meta/counter tactics to emerge. Eg. Compare the Korean War to the Vietnam War and the emergence of Asymmetric Warfare.

tldr; I think alien weapons technology being suddenly nerfed best fits your requirements. Eg. The latest opponent are immune or the weapons' can no longer function (blackhole tech is running dry). The enemies don't even need have to be more technologically advanced or sapient - see the Great Emu War

• Even if their weapons aren't working, if they have advanced civilization they have lots of stuff that can be used as weapons. High power exhaust from engines, power cores blowing up, teleportation tech teleporting only half of enemy body away, scanners amplified to work as death rays (did you see what happens with birds when they fly past radar?) etc... You can't be "advanced" and "weak" at the same time - that's pretty much antonyms. Being "advanced" gives your more means to "rearrange" world by definition. That includes all the funny ways to "rearrange" matter that your enemies made of. – Oleg V. Volkov Oct 4 '19 at 22:20

Other answers have addressed conflict and battle, but these are not war. It's reasonable for a society to have experienced violence and conflict without having to go through the trauma of regearing their society for total warfare.

Their ships are not unarmed, their soldiers not untrained. They have had border skirmishes, they have encountered pirates and raiders, perhaps they have had to subdue rebellious provinces, but these things are still not total war.

Total war

Total war is warfare that includes any and all civilian-associated resources and infrastructure as legitimate military targets, mobilizes all of the resources of society to fight the war, and gives priority to warfare over non-combatant needs. The Oxford Living Dictionaries defines "total war" as "A war that is unrestricted in terms of the weapons used, the territory or combatants involved, or the objectives pursued, especially one in which the laws of war are disregarded."

In the mid-19th century, scholars identified "total war" as a separate class of warfare. In a total war, to an extent inapplicable in less total conflicts, the differentiation between combatants and non-combatants diminishes, sometimes even vanishing entirely, due to the capacity of opposing sides to consider nearly every human resource, even that of non-combatants, to be a part of the war effort.

This may be where human experience over the first half of the 20th century comes into its own.

Total war changes everything, especially mindset.

Total war isn't just two armies fighting to victory, it's two entire societies facing off. Everything one can bring to the field against everything the other can bring. To a society that has long managed to have total separation of military and civilian considerations this may require external expertise. Their military production is sufficient for normal use but they don't understand that they need to turn everything over to military production. They have to consider how the skills of every single member of the society can help to bring victory.

It's also possible that a society that has long held a technological superiority over their neighbours has not developed the cunning required to face off against an equally matched or superior foe. They're honest and open rather than underhanded and deceptive. They don't understand the use of spies, and sabotage or the need to defend yourself against them.

The aliens they are fighting are more similar to humans (and use human style tactics, warfare, and psychology), than who they usually fight against

Perhaps this alien species is not peaceful per se (they regularly fight within their world or with other alien species) BUT they have never encountered an enemy like this. Warfare changes a lot depending of the technology available, the terrain/environment, mindset/psychology of the people, motivations for the war etc. Think how damaging guerrilla warfare was when previous battles had been two large groups fighting head on. It would be good to learn about defending agains guerrilla warfare from people who are experienced with it rather than learn about it through trial and error. And what about the psychology of other aliens - I'd imagine the concept a kamikaze was not something that the USA predicted. Perhaps the aliens they are fighting are more like humans and they want to know what they are capable of, or where their weaknesses are (like demoralization or propaganda which may have no effect on their population)

Yes, it's totally possible. Human warfare is a deeply human concept. Sure, some primates show similar behaviour, but that's about it.

Our evolution rewared this behavaviour, obviously. But that's our evolution, another species could have evolved to a point where they are unable to form large cohesive groups necessary to fight wars. Our a thousand other things could be different, e.g. a strong pack mentality, where leaders fight and the rest submits.

Even if they are psychologically capable of conducting something like warfare we would understand, they could choose not to do so:

• Their latest few centuries of advancement discouraged conflict, e.g. because they have evrything the need not to fight over something. Conflict due to societal differences is solved in another way.
• They conduct warfare according to their own rules, which are just different to human rules - so they have no idea to fight us effectively.
• Their society actively suppresses the institutions necessary to fight wars to avoid having to fight them.

And a thousand other possibilties.

The key to recognize here is that aliens are alien - they evolved differently, they have different bodies, minds and history. It is absurd to think that they will solve conflicts the same way as modern human societies (modern warfare is a recent innovation). What you need to do is to find a group of causes that leads to your desired outcome (clueless in war), without beeing unbelievable to the reader. If you humanize them to much, the reader will not believe you but if you explain what's different about them the reader will believe you.

• Lolwat? Pretty much each species have its own way to drive other families or individuals of same species from their living room. Lions kill lions, dolphins kill dolphins, etc. – Oleg V. Volkov Oct 4 '19 at 16:50
• @OlegV.Volkov Thats conflict, not war. Lions kill other lions, but they do not really organize large groups for it. Many social animals devloped techniques to solve status questions without bloodshet. – Christian Sauer Oct 4 '19 at 21:14
• They do. nypost.com/2018/09/07/… And many other species kill in packs all the time. Many species kill not only to eat, but for different reasons, like preserving their own prefered environment. And yes they do that in packs too. What is this if not war? – Oleg V. Volkov Oct 4 '19 at 22:27
• Here's one more article. Check the title: news.bbc.co.uk/earth/hi/earth_news/newsid_8120000/8120712.stm. It explicitly says about lions making group to win a war. We're simply used to use "war" for human conflicts, but there's nothing in "war" that is "deeply human concept". – Oleg V. Volkov Oct 4 '19 at 22:31

Psychological Reasons

The galaxy is not as rough a place as Earth. Earth is a massive outlier on how hardcore an environment it is to evolve in. Here, everything is trying to kill us, from the microbes in our bodies to the corrosive oxygen we breath, the universal solvent of water that permeats everything. The competitive plantlife that chokes its neighbours and animals that hunt and prey on each other.
Our world is a brutal and savage place, not for the faint of heart. It's easy to forget that when we live in the controlled environments of towns and cities.
Our ancestors knew better.

As consequence of living in such a lethally dangerous place, we've developed many instincts, some of which aren't so good for peaceful society. Notably, we tend to form tribes, and other tribes are automatically "Other" in our minds, enemies at worst, strangers or acquaintances at best.
What we don't know can kill us, the unknown cannot be trusted, and is there any place more alien than another man's mind?

This sets the tone for large groups of likeminded people to be naturally pitted against other groups of people. Scaled up, that turns to warfare.

On a more peaceful world, tribalism is much less of a strong instinct because it hasn't been necessary to think that way, your aliens don't so reflexively divide the world into "us and them". They still develop enmities and rivalries, but generally they cooperate better than we do in large groups.

The upshot is, they have little experience with warfare among their own kind. It's simply not in their mindset to look at another large group of people as a collective enemy.

The nearest they might come would be teams of people who fend off single wild animals, or hunt down criminals and psychopaths.

Ultimately, your aliens are a more cooperative and peaceful race, open minded and friendly to strangers.
Natural explorers rather than conquerors.

Utterly unprepared for an aggressive and irrational foe to attack them.
Thank goodness they have Utter Vicious Untrusting Bastards like us to help!

• The galaxy IS a rough place just because of physics. There's meteorites flying around, mountains falling down on you, lava waves heading at your explorers. If they're "advanced", obviously they did learn how to negate outside destructive force or remove it completely. What would make humans different kind of destructive force? – Oleg V. Volkov Oct 4 '19 at 22:39

They figured out Replicators early on

One of this society's first major achievements was Star Trek-style replicators. These have been developed now for millennia, and are cheap, ubiquitous, and require almost no power or resources to operate (or the power and resources are also cheap and abundant).

This creates a post-scarcity world, where anybody can have anything they want whenever they want just by pushing a few buttons. Food, medicine, clothing, heck even building components can be created for basically nothing. This eliminates need-based crime. Why steal anything when you can get what you want for free?

It also removes the incentive for predatory business practices. Most big companies today care only about their bottom line and how much money they can return to their investors. In a world where money has no value, this sort of thing would disappear. Big companies would only exist to work together to build the things that can't be created for next to nothing by any kid with a replicator.

This would include the ability to travel off-world, which might become a necessity since a world without scarcity could face problems of over-population. (Though not the usual problems since most resources are free). The biggest problem would simply be lack of space, and the only way to get more space after a while would be to leave the planet. Assuming there are no hostile space-faring neighbors in their neck of the galaxy, it might not even occur to them to develop weapons.

Their next priority would be in terraforming. Let's say they have a nearby Mars-like planet just as we do. Well, all of the problems that we would have colonizing Mars wouldn't be an issue if you've got ubiquitous replicators. Start by dropping a few off all around the planet, programmed to do nothing but pump out breathable air. Eventually, you've got yourself a livable atmosphere, and you can replicate yourself some buildings (in pieces if necessary) and enough food to feed your colony. Boom, you're now a multi-planet species.

A few millennia later once they've colonized every rock in their solar system, they might start looking further abroad. This is when they begin to develop wormhole technology. In this entire time, they've never encountered anything hostile, and never needed to develop weapons or military capabilities. This is where your story might start...

• I'd say knowing how to terraform Earth and making those pesky humans unable to continue existing still counts as "being good at war". If your enemy is WAAAAAAY better at rearanging physical matter - he's way better at war than you by definition. Setting up replicators on low orbit and dropping heavy stuff down non-stop counts too. – Oleg V. Volkov Oct 4 '19 at 22:35

Physical weakness

The species has grown weak in favor of more intelligence. Think of the descriptions of H.G. Wells in his book "The War of the Worlds":

Based on their physical features, the Martians might be the descendants of a species similar to human beings, that evolution has reduced to only a large brain and head and two groupings of eight tentacles (hands). They are described as sluggish under terrestrial gravity, heavier than on Mars. It is reported that several Martians attempt to "stand" on their tentacles, implying that they are capable of locomotion in this manner while in Mars' lighter gravity, but not on Earth.

You could think of the species being used to very low gravity worlds, while their adversary is based on earth-like gravity worlds. Thus they need humans to do their best; storm the gates. Perhaps in exchange for some technological favors.

• Not really. Humans are already using drones in warfare. A more advanced race could build more advanced drones and not need to risk themselves. – Thorne Oct 4 '19 at 6:49
• Come on, they have wormholes! Why would they need to get physical if they can simply open one in the middle of Earth? – Oleg V. Volkov Oct 4 '19 at 22:24

Maybe they were so powerful that nobody dared to challenge them military-wise for a long time. Neither did they go to war since it was easier for them to pursue their goals diplomatically or economically.

Then, one day, they had to enter a military conflict, only to recognize that they are deeply incapable of efficient warfare for a long time. Their army is ritualized and those rituals do not add up to victories.

They don't need to be bad at it, they just need to be worse than the other guy.

What are "good tactics?" Good tactics are tactics that help you win. It's entirely possible that these tactics worked quite well for the first alien species when it only went to war with itself-- but the moment they encountered an outside force, these tactics no longer worked.

So basically, species A and B go to war. Species A tries a certain tactic, the winning strategy on their world. Species B already had a clever solution, and employed it. Species A is unable to come up with a response, because Species B strategy had, until that point, been considered bad strategy.

As to why Species A thinks Earth can help is beyond my guess, it seems to me that warfare in space is something we'd be clueless on. Unless of course, species A has had their planet invaded already, in which case, Russia can definitely help you repel an invasion. Just ask Carolus Rex, Napoleon, Kaiser Wilhelm II, and Adolf Hitler.

No. It's is completely impossible. If they were bad at winning against other threats, they wouldn't be alive to reach that "advanced" state. Not a single advanced society ever lost a war to a lesser one. Fight there and there maybe - but never a war. That's valid not only for humans, but also for animals: not a single smarter and more powerful species lost a war to weaker one. Because you know, that's pretty much definition of being "strong" and "advanced".

The single reason your aliens could be bad at conventional "human" warfare is because they're so far above that they don't need it and can annihilate or at least block all harm from lower races without such trivial approach.

It's pretty much same as some guy sitting at keyboard and controlling a drone could be dozens of years behind some native savage in archery, swordsmanship, muscle mass, ability to build devious jungle traps and whatever else other savage military-related terms. Is that thin wimpy nerd obviously pathetic warrior to strong musclebound guy with a big club? Of course he is, yet he is far better at war because he can "defeat" entire tribe with a single move of finger touching the button.

Obviously you cold paint aliens at being this kind of "bad at war", but I doubt this will actually help their enemies much.

There is actually historical prescience for exactly this.

Ancient Sumer was the first human civilization ever. Without any other peoples to interact with, the people of Sumer lived for over a thousand years without developing an idea of warfare. This ended up being their downfall, as when other civilizations began to appear near their border they were invaded without being able to put up much resistance. Their main attempt at defence was the creation of a wall which was not anchored at any natural barrier, which resulted in their invaders simply walking around it.

If you were to follow a similar path where in a culture never encounters another, then they may never develop war as an idea. Even a civil war is unlikely if the ideas such armies have not been created. Now this does not guarantee against violent actions within society such as fighting, murder, or assassination, nor does it prevent things such as gang warfare, but traditional large scale warfare is unlikely.

Make them too selfish and decadent to fight

Use modern wealthy, urban and liberal elites and expand on that. Ancestors of your alien species were once great warriors, conquerors, explorers. They were fearless, cunning and ruthless and created great empire with enormous technological knowledge. No one could challenge them, so no one did ... Lot of time passed.

Your present aliens, bask in the glory of their forefathers. They do not have to struggle for anything. Droids, or slave species genetically engineered to serve, attend to their every need. Medicine is so advanced that they live almost indefinitely. They do not have a need to procreate, so most of them are childless and care mostly about themselves and own whims. Having long lives and great intelligence, they are very educated, they know art, cuisine (or their equivalence of it), all kinds of "noble" pleasures and pass times. They sometimes engage in philosophical debates to impress each other, but all of this is mostly fruitless.

Suddenly, a new species arrives. They are relatively primitive and unintelligent (at least their foot soldiers) , but numerous and ready to sacrifice themselves. You could invent some "holy cause" for them to wage war against our aliens. Our aliens of course know theoretically what has to be done. They first attempt to create army out of their droids/slaves, but that does not work - they are either too docile or too unintelligent to operate alone. This means that some of our aliens have to serve as officers in this army, and risk their lives for their entire species and civilization. And being what they are, they could not find the fools for the job.

Therefore, they have decided to find suitable mercenaries and humans fit the description. Humans have solid understanding of military organization, aliens furnished them with some of their technology and gave them portion of their slaves/droids . Aliens also manipulate situation to present newly arrived aggressive species as a threat for humanity, giving another reason to fight. There could be even backup plan for aliens, where they find another group of mercenaries beside humans, in case of human failure or if humans become too strong.