"Good guys" committing perfidy (fake surrender) and it's treated as a clever heroic ploy instead of a war crime or something morally dubious

[u/AporiaParadox]

1. Star Wars: The Clone Wars. Anakin pretends to surrender to the enemy multiple times during the Clone Wars. And no, it's not used to indicate that Anakin is falling to the Dark Side, other characters like Obi-Wan do it too.
2. The Iliad. The Trojan Horse was a real dick move, a fake surrender compounded by a fake peace offering, followed by a massacre. I get that it was a different time, but still, most modern adaptations just treat it as a cool thing. One thing I'll give Nolan's The Odyssey credit for is that Odysseus recognizes that what his "clever plot" was wrong.

Perfidy is a serious war crime, because morality aside, in exchange for one victory, you're dooming all of your allies who might want to legitimately surrender in the future because now the enemy is just going to execute them, not to mention that now the enemy won't surrender to you and will just fight harder.

[u/NinjaOfOnion]

Im pretty sure there’s no Geneva Convention in space or in ancient times

Edit: To be honest, this wasn’t supposed to be a serious comment, just a play on “they can’t violate the Geneva Convention because it doesn’t exist” though I do now know of it’s equivalent, Yavin Code, so I learned something from this 

[u/Murmido → u/NinjaOfOnion]

Its not about morality or legality. As OP explained doing this means eliminating the possibility of a peaceful surrender in the future.

How is an enemy supposed to trust you if your army frequently pretends to surrender before going for the kill? The only safe solution now is to just execute everyone even when they are at your mercy.

[u/RedditOfUnusualSize → u/Murmido]

Exactly. Perfidy has been understood to be a war crime since long before the Geneva Conventions. It's not a war crime because the law says it is. It's a war crime because reciprocity is a thing that exists in human behavior.

Put simply, you want the enemy to trust that your surrenders are honest, because if they don't, then they stop accepting surrenders. And then if you are on the losing side, they just massacre every person on the losing side to the last man, on the assumption that by doing so, they are preventing you from double-crossing them. You want the option to surrender and survive the war even if you are on the losing side? Narrator's note: you absolutely do want that. Well, then it is in your interest to rigorously enforce rules about perfidy on your own side, and rigorously punish violations of perfidy by everyone who commits it.

That's how war crimes work. You don't need a legal code and an international tribunal to make it work. You just need both sides to understand the concept of Prisoner's Dilemma.

[u/Basilus88 → u/RedditOfUnusualSize]

Yeah people who think that war crimes and crimes against humanity were somehow discovered in the XX century in a town named Geneva or by an organization called the United Nations are just flat out wrong on every level.

Rules of engagement, what it means to be an honorable soldier or warrior and the meaning of "just" war were discussed as long as humans existed and fought each other (so basically forever).

It makes plenty of sense for a "Geneva convention" to exist in basically every setting, be it fantasy or Sci-Fi. It won't be called that and it might not even be codified or written down but it's definitely there.

[u/Aickavon → u/Basilus88]

Hell, even in ancient times there were rules for engagement and and announcements on WHAT kind of war you’re declaring on your opponent.