So I'm setting up an invasion of the country my story is set in. I've got all the worldbuilding info I could need - how many soldiers are at each base, how many occupying forces it would need to capture each civilian city, etc - I only have one thing remaining: determining when my commanders will give up. So, imagine you're the commander of a base at which you command roughly 10,000 soldiers. To set the scene, in this fictional world, this nation has a technology level roughly akin to our late Renaissance or early Enlightenment periods, except with one notable difference: few cannons, and no firearms, because the natural resources used to make gunpowder are rare. So our army still carries swords and bows, and our nation's navy consists of wooden sailing ships which fire essentially an oversized crossbow instead of a cannon to pierce enemy ship hulls, and you have never seen any type of aircraft in your life. Then along comes your new enemy: where we've got sailing ships, they've got steam-powered ones. Theirs have metal-armored hulls. They have proper cannons, many of them, with which they rip our nation's navy to shreds. Then the ground troops land. Many of them still carry swords and bows, but they are simply better. That's to say nothing of their firearms: where the oxidizer for gunpowder is rare naturally, they have the breakthrough ability to produce it artificially, allowing them to arm their invasion spearhead with rudimentary rifles. You look up to the sky and you see rigid airships - you've never even heard of such a thing - and on their suspended decks they, too, carry firearms: crew-staffed repeating guns that go RA-TA-TA-TA-TA-TA raining death from above, their terror making up for the ships' slow pace. So according to my research, the conventional formula is 1 defender = 3 attackers, but these circumstances are far from conventional. Is there perhaps a historical example I can look to of an army going up against an enemy so much more advanced? What proportion did they lose before giving up? Did they even attempt to fight, or was the sheer shock of their enemy's technology enough to make them submit? And if it were you: How many of your 10,000 soldiers are you willing to lose to this enemy? How many of them would it take to make you decide it's not worth it to even try?
Any of the battles in most colonial wars. For example: https://en.wikipedia.org/wiki/Fall_of_Tenochtitlan 1300 Spanish and 200,000 natives vs 300,000 Aztec defenders. 100,000 Aztecs killed before the city fell.
So they had a roughly 3 to 2 numerical advantage, but lost a third of their forces to a superior foe before surrendering. If I follow this example, this base's commander might only be willing to sacrifice a little over 3,000 of his 10K soldiers. That would be after watching two cities in the invasion path fall first, and a third one being fought over concurrently with this base. That sounds about right in my opinion, and it allows for a large number to surrender while also allowing a sizable minority to escape and join the resistance later.
It depends on the intention of the enemy. What awaits you when you surrender? If surrender means death for most of the defenders you will fight till the end. Is "asymmetrical warfare" an option? Our real world tells us that even if the intruder has superior technology it can be surprisingly difficult to accomplish victory if the defender has the ability to get "in the underground" and use sting operations instead of open war. Can the defender use his good knowledge of his own territory? Or the size of his territory? (like Napoleon vs. Zar or 3rd Reich vs. Soviet Union) Does the defender have time to prepare? I could imagine that a modified trebuchet can be used as quite effective air defense against slow moving rigid airships. Hitting a hydrogen-filled airship with incendiary projectiles would give a nice special effects scene... If there is time to build fortifications - and you know which fortifications you need - you can hold a position even outnumbered in headcount for prolonged time.
It’s worth pointing out that translating force ratios directly into troop numbers requires something close to parity in technology, troop quality, and officer competency. If there’s a significant imbalance in these factors, they don’t apply very well. I don’t know if there are any historical examples where the tech difference is quite this stark, since most of the colonial wars were fought before airpower came into play. Certainly not enough to shock native defenders into rolling over without a fight. You’ve got wide gaps with: The later Indian Wars (1850-1924) The Opium Wars The Boxer Rebellion Anglo-Zulu War and other wars of colonization in Africa First Italo-Ethiopian War Second Italo-Ethiopian War Even when you’re looking at forces with Stone Age tech and imported guns, the defenders still fight (and sometimes win). If defending forces are surrendering without a fight, it’s probably because the situation is collapsing around them rather than just from shock at the technology. In terms of how many casualties this commander is willing to take, this will depend on factors ranging from the commander’s temperament to how much he knows about the big picture and how quickly the enemy can kill his forces. He may commit his troops to battle and suffer atrocious losses in a few minutes. Unless we’re talking about fanatically devoted soldiers, I doubt you’re looking at more than 50% casualties before surrender or a complete rout, and I only leave the figure so high because Late 19th/Early 20th century artillery and early machine guns could inflict heavy losses very quickly against “primitive” opponents. Somewhere between a quarter and a third is more typical.
The OP hasn't said very much about who the commander is, as a person. This is important enough in real battles, but in fiction the commander's character is the only thing with potential to matter to the reader... whereas 1,000, or 10,000, or 100,000 or umpty-million make-believe people dying in an imaginary battle between two pretend countries probably won't matter to the reader. When we read about the death-toll in a real battle, it affects us because it happened in our world. The death toll in an entirely speculative fantasy or sci-fi battle isn't able to matter that way. It's only like Darth Vader blowing up Alderaan (whose population apparently was 2 billion, if anybody cares): to the audience it's pretty much a special effect, and if it's anything more than a special effect it's only thanks to the character-acting. So the OP's commander could on the one hand be like Leonidas and endure 100% casualties to give his civilization the best possible chance (and the reader the most memes), or he might be retreat out of a complex and nuanced realism established over the course of the story - like Kutuzov.
https://en.wikipedia.org/wiki/Zulu_(1964_film) The actual story: https://en.wikipedia.org/wiki/Battle_of_Rorke%27s_Drift
Everyone has brought up interesting points to consider, but this especially stands out since the commander himself won't actually be a character in the story, more like his actions are referenced in the story because they determine the course of the battle, but nonetheless you make it clear that I still must consider his character even if he doesn't outright appear. Ultimately I think what would work best for my story is that he puts up a brave and determined fight for a good long while, but eventually is surrounded and in the fog of war he thinks he has suffered greater casualties than he in fact has, and so he surrenders thinking the battle situation is more grim than it is - understandable, given the enemy's technology advantage. This leaves the base mostly intact for the occupied forces to utilize, but results in it being under-defended by them, a fact later exploited by the insurgency when they regroup and get a better sense for the actual situation.
You haven't mentioned what kind of communication exists between the two armies and what the motivations are of the technologically advanced one. In other words, what terms would they be surrendering to? Is it 'well, we won't annihilate you today with our advanced technology...' or something worth considering?
If I were the commander, I would not consider a suicidal last stand. That's great for stories, not so much if you want to win. What you do is go total insurgency. You blockade roads, destroy bridges, conduct night attacks where mostly silent bows can still be quite effective. Do your best to poison their food and water. Even your rudimentary weapons can be used to slowly build a cache of better ones stolen from the enemies who are taken out one by one. Find out powers the airships (steam?) and find a way to contaminate it with kerosene or the like. Really the possibilities are endless of the problems you could present an invader and with 10,000 troops you can convert into an effective guerilla organization...yeah the enemy is going to be in for a long miserable occupation.
Yep, exactly, that's what the next part of the story is about! Part 1 develops my characters, Part 2 sees their nation fall, then Part 3 is about my characters waging an insurgency war - exactly as you describe! The superior force is primarily concerned with resources: they've built a society dependent on their latest technological developments, but they lack the resources at home to sustain that technology long term. As long as they can be left to conduct large-scale mining operations in my nation's northern deserts and mountains, they don't so much care if opposition still exists so long as they feel they can keep it subdued -- as Joe pointed out, though, that's where their trouble will lie! As for collaborators, they may actually get a decent deal, perhaps by keeping their former positions of authority under an occupation government, or by taking the newly-vacated positions above them. Doesn't matter the tech level or time period, most people can be bribed with a promotion of status! A select few may even get a cut of the spoils from that mining. By and large, though, most will remain loyal to their nation and will form the basis of an insurgency. I think I now have a better sense of the scope of this invasion, as well as key problems I can account for in the enemy's planning that will lead to their later defeat at the hands of my characters. It's clear to me now that I can realistically portray this at first as a decisive victory for the invaders, but then later reveal it as a misplanned strategic folly that was doomed from the start.
I don't think you can determine the point of surrender based on number proportions. It is far more determined by the cultural background of both sides, their commanders and the personality of the commanders along with the greater context of the confrontation. Napoleonic examples: Kutuzov regularly retreated from battles he wasn't explicitly certain he could win. Which ... were a lot of battles, in fact. The Russians retreated before the Ulm campaign, before the Jena-Auerstedt battles. If your defending army was as obedient as Kutuzov's, and your commander as careful as he was, then they wouldn't even fight. Conversely, Kutuzov's retreat aggravated Tsar Alexander greatly and he insisted on continued fight during the battle of Austerlitz. The opposite of Kutuzov, he was hot-headed and inexperienced and therefore gave the orders to retreat far too late, and the order was impossible to execute as by the time it reached the Russian left flank they were enveloped by French cavalry. Hence their retreat suffered grievous losses. The battle of Fuengirola is an example of no-grounds-given by Polish troops who were bound by "death before dishonor" and unparalleled dedication/loyalty. The formula there for the first day was 1 defender = 63 attackers, not counting the fact the defenders had nigh three cannons they didn't know how to use whereas the attackers had a support fleet (including two battleships of the line). The battle of Auerstedt saw Marshal Davout outnumbered two-to-one with a single corps against the main Prussian army - despite that, the Iron Marshal commanded his troops to hold ground, engaged the Prussians and miraculously defeated them. Whole wars & confrontations: The seven years' war saw the Prussians outnumbered five-to-one on the continent, yet they kept up the fight with confidence and concentrated on defeating the enemy in detail. The Napoleonic wars & revolutionary wars regularly saw the French outnumbered two-to-one, yet they never relented, instead going on the conquest. A good illustration is Robespierre's speech on total war, and the lengths to which a nation can go to refuse defeat. Robespierre had an intriguing speech on total war, declaring all assets of France as part of a war machine & all men and women part of the army to protect the revolution - that kind of attitude can keep a whole nation fighting, refusing to surrender. It's the concept of Total War; it's what turns small confrontations of a few battles (see Prussian-Austrian war) into major confrontations where eradication and complete defeat is the key (like the Napoleonic wars or WW2). In light of the latter, the context of the confrontation should also be mentioned. Berlin's garrison surrendered to Joachim Murat, even though they were less outnumbered than the German garrison in 1945 - the main difference being the context where Napoleon's enemies lived with the assurance they'd be given terms & could lose some territories but live on unchanged (hint: that didn't happen, and caused resentment that later led to Prussian defection to Russia). In contrast, the Nazi garrison faced total extermination of their cause, leadership held responsible for myriad war crimes and the fall of their conceptualized world order. If your defenders are accustomed to warfare where prisoners are treated fair and where diplomacy triumphs in moderate peace treaties, they might easily give ground. If they face genocidal enemies whose goal is total and complete eradication and fundamental change to world order, they will never surrender. There is a good reason Britain never surrendered to Germany - the British weren't only prepared to fight outnumbered three-to-one against superior technology, they were ready to keep on fighting even after defeat and after occupation - hence the famous speech from Churchill.
As a consideration of how much personality plays in such decisions, consider the difference between Col Travis at the Alamo vs Col Fannin at Goliad, 90 miles away. The former (and his compatriots) essentially fought to the last man, while Fannin surrendered and his command was still wiped out by Santa Anna. You can also research the fighting between Native American nations and the US Army in the port Civil War period.
It really depends on a whole lot of variables- the politics and culture of the defenders and their society would be pretty key to consider, as well as their leadership and morale. In 2014 1,500 Daesh fighters attacked Mosul with ~30,000 well-armed, but very demoralized and badly led, defenders. The Iraqi army simply collapsed after a few days, with mass desertions and routs.
@JadeX Many good comments here, to which I would like to add my paltry one. As an ex-military man myself, I would think determining the degree of success the defenders would have, which would influence their possibility of victory, depends largely on two things. The first you address with your attacker/defender ratio. Usually the first thing commanders look at. The second is topology. Looking at the Battle of Thermopylae, the Greeks were largely successful due to the topology of the area where the battle was fought. They ended up losing in the end, but held off anywhere between 70,000-300,000 Persians for 3 days, killing in excess of 20,000. Topology matters. So if the attacking force outnumbers the defenders, and the topology is not in your favor, an earlier surrender might be in order. Of course, if the defenders will be killed after surrendering anyway, then never surrender.
What awaits after surrender? Will they march in and murder us anyway? Then we may as well fight to the end and take as many of them with us as we can. If it's an "honorable" war you surrender when the commander realizes he's wasting lives in a hopeless situation. I'm already surrounded and hard-pressed, low on everything except dead and wounded. When I saw that army of enemy reinforcements coming in from the east, and yet another from the south, it sort of convinced me that surrender might be a good idea. Let's hope they honor the terms of surrender.
If defeat is pretty certain, then wouldn't it be a good idea for the whole army to just peace out? I guess it depends on how strategically important the fort is.
