I think wars happen because of perceived existential threats, genocide happens because of believing some people are subbuman.

Animals are subhuman. We don't feel the urge to kill them for this reason. Slaves were certainly considered subhuman, and Europe was not on a mission to kill them all.

Wars might be caused by disputes about borders, or by greed. They don't require the elimination of the enemy, just its defeat. But at least some of the better known genocides and mass murders are caused by the perception in the mind of the perpetrators that the very existence of the victims is an existential threat to them.

You are obviously correct that we don't just kill things because they are subhuman, but it sure makes the threshold for deciding to kill things lower. We generally kill animals very differently than the way we kill humans, particularly pests. Animals are often killed when they pose the slightest risk to humans.

Killing women and children could only ever seem appropriate if one thought that the women and children deserved as much consideration as a wild animal. I think it's the same with slaves in a lot of time periods. They didn't kill them for fun, but they also didn't get charged with murder when they did kill them.

Between killing enemy combatants and killing pests, genocide tends to look a lot more like killing pests.

I think we agree, more or less. Now, to add a corollary to this discussion, consider that existential threats are usually perceived, if not necessarily as sub-human, as non-human. Because somebody who doesn't just disagree with you on some issues but wants to destroy you must be necessarily lacking some fundamental human quality.

So once you've set a narrative of the "it's us or them" type, it's easy to place the blame of your necessary defensive action on the enemy: because the enemy has already renounced its humanity when it set itself on enslaving or destroying you.

This sounds like a cartoon version of what would lead to a genocide. It seems like this sort of thing is usually the product of close proximity, prolonged ethnic conflict, a perceived threat (real or imagined), and other pressures like lack of resources.

Well from what we read about the genocide in Bosnia, the ethnic conflict was purely made up over a period of just a few years prior to the genocide. The party in power in Serbia latched onto a massacre that had been perpetrated by the Ottomans hundreds of years before as a way to whip up sentiment against the Muslims. Economics definitely came into it, but there were lots of anecdotes of people who didn't even know what side they were on and had to literally ask their parents about their heritage to find out whether they should fear for their lives.

In Rwanda, the divisions were constructed by the people running the colonies and hadn't actually been divisions recognized by the people prior to that. That happened over a period of decades, sure, but they were also complete fabrications that turned into reasons to kill people who were called "cockroaches" over the state run radio.

I agree that dehumanization isn't the only factor, but it's also not cartoonish. People kill each other all the time for all sorts of terrible reasons, but what causes them to crowd a bunch of women and children into a building and set it on fire is a belief that those people are less than human.

Once again, I'm not talking about war, I'm talking about genocide.

Edit for clarification: a lot of the things you mentioned are very often present, but in that class we read about the genocides in Turkey/Armenia, Bosnia, Rwanda, Cambodia and Germany, and it was striking how similar the language was from place to place. Despite the different cultural, economic, and historical circumstances, the one thing they all had in common was really brutal language about the targeted group. We've all seen the propaganda targeted at Jews in Germany, and I mentioned above the Rwandan radio calling people cockroaches. This attitude toward the opponent is necessary but not sufficient.

Red Terror was entirely about a perceived existential threats, and didn't make any claims of sub-humanity of those targeted. Was it not a genocide?

This is a quote from the wikipedia page about the Red Terror, from the chief of the Ukrainian Cheka:

"Do not look in the file of incriminating evidence to see whether or not the accused rose up against the Soviets with arms or words. Ask him instead to which class he belongs, what is his background, his education, his profession. These are the questions that will determine the fate of the accused. That is the meaning and essence of the Red Terror."

You're right, it's not literally saying they're subhuman, but it seems pretty close. Actions are irrelevant, only identity matters. That doesn't have anything to do with perceived threats. Only a crazy person would think that someone of a certain class was a threat regardless of their actions unless they believed that there were implicit differences that basically amounted to those of different class not deserving life. And yeah I think it's definitely a genocide.

It's very similar to the genocide in Cambodia where they killed people who wore glasses (in addition to all the others) because they assumed that if they wore glasses it must be because they were literate, and all intellectuals were the enemies of the working class. We read an account of a man who had been a leftist but was sent to a camp because of his glasses. Once again, they didn't literally say people were subhuman, but they sought to attribute fundamental differences to something as superficial as eyesight.

In my first comment, I was mostly talking about people coming to believe that a group of people was fundamentally different in a way that common decency no longer applies, that you no longer give them even the consideration you would give criminals, you just send them off to die because they are irredeemable for something as stupid as what family they were born into or whether or not they wore glasses.

Class, education, profession are mostly about actions, actually. They just happen to be identities that are established by those actions. And (early) Soviets didn't consider any of that irredeemable either, as evidenced by many Imperial "white officers" later in employ of the Red Army.

So, no, it wasn't about any kind of a fundamental difference. That ideology didn't believe that there was any group of people to which common decency no longer applies. They believed that common decency no longer applies to anyone, because revolutionary necessity requires it. People who were deemed dangerous to that necessity were killed not because they were deemed subhuman, but solely because they were deemed to be a danger. They even reflected it in the criminal code - it didn't speak of "punishment", but rather of "means of social protection", and death penalty was euphemistically referred to as "the highest measure of social protection".

Thanks for the detailed reply. You seem far more knowledgeable about this than I!

No the Red Terror was not a genocide any more than the Civil War was a genocide. Conflating the two doesn't make much sense.

I think mass murder of civilians on the basis of socioeconomic class is pretty damn close to a genocide, and definitely different than the Civil War, even though a lot of civilians died in the Civil War.

Words have meanings, and just because masses of people are murdered doesn't mean its genocide just like the Civil War or any war. The reason I've stated elsewhere in this thread is that people want to use genocide with regards to authoritarian left states is a tactic by fascists to soften the horrors of the Nazism.

The Stalinist regime was plenty violent and systematically kills millions of people, but calling it genocide doesn't make sense because that wasn't what it was by definition unless you want to compare it to Nazi germany which killed millions more.

Stalinist regime did plenty of outright genocides even by the most rigid definition of the word, even if you insist that it's not any mass murder, but one carried out on the basis of ethnicity. Technically, most of those were designates as "population transfer" (i.e. deportations) - but they were often carried out in a way that either deliberately caused casualties, or knowingly did nothing about the ones that were the inevitable byproduct of the implementation. For example, the mortality rate for Chechen and Ingush deportees was around 25% - that's literally hundreds of thousands of people; and in some cases, entire villages were massacred outright because deporting them was not deemed logistically viable. All those people suffered for their ethnicity and no other reason. If that's not a genocide, what is?

But anyway, originally we were talking about "the worst atrocities in the history of the world", not genocide specifically. So it's reasonable to assume that genocide in this context is used in a colloquial meaning - i.e. any kind of intentional mass murder by some group metric, not necessarily ethnicity.

Also include the simple motivation of greed. A lot of war and genocide is simply about profiteering. Some perpetrators do so knowingly. Other miscreants feel need to invent some excuse, such as dehumanization, and repaint their predation in righteousness.