The United States engaged in an internal war between citizens beginning in 1860 and ending in 1865. I was born only about 80 years after the end of that war...so this is not like ancient history...this war wasn't fought between Sparta and Athens several thousand years ago. The last (known) participant in that 'civil' war died several years after I was born...if I had known him I could have had a conversation with him.
This incredibly bloody conflict was over whether human animals could be considered the property of other human animals. Apologists for human slavery have tried to make the issue of "union" and "states rights" be placed at the center of the cause of the conflict but if you look at the reason behind those states wanting to leave the union you discover it was because they were afraid they were going to lose the "right" to legally own other humans. And the "states rights" referenced consisted of the "right" to own human beings as slaves.
"Incredibly bloody" refers to the fact that more than 2% of the population was killed in that war. In 1860 there were around 30 million people in the U.S., the civil war resulted in about 620,000 deaths, this compares with WWII where the U.S. had a population of about 142 million people and about 400,000 were killed...which works out to about .0028% of the population.
Why think about the civil war in context of WWII? Well, upon reflection, one of the major notions driving the Hitlerite dictatorship was that human animals could be enslaved and/or exterminated and had no "rights" just because they belonged to a particular group (neither was that kind of thinking unknown to the Tojo government of Japan). A big factor motivating the German/Japan governments was the notion that some human animals were better (or more worthy or whatever) than other human animals...depending on what group they belong to. That kind of thinking seems awfully similar to the thinking of the Confederate state governments.
WWII definitely isn't ancient history...and by the way...the U.S. was still practicing legal segregation while it was fighting the Axis powers. In other words, we were fighting against those advocating slavery while saying that some of our citizens were not worthy of some "rights" simply because they belonged to this or that group...but we didn't enslave them (hooray for us, I suppose).
It's all about the equality thing. We (those of us who are human animals) seem to have really serious difficulties with the idea that we (all human animals) are equal (in terms of our right to life, liberty and so on) to one another. Some of us are audacious enough to envision that equality notion (the right to life and liberty thingee) as applying to all living beings. We are called vegans.
And, for all of us who are vegan, it might behoove us to realize that we're on the side of a cause (equality of the right to live life freely for all living beings) that has prompted a lot of resistance when it was applied to just one group of animals (human ones), much less all animals.
It makes me wonder what might be in store for the future. It's obvious that human animals are willing to kill or be killed to enslave other human animals...that makes me wonder what they might be willing to do to continue to enslave non-human animals. It's sort of spooky.
So, for you who are vegan, the next time someone gets irate and/or upset at your advancing the notion of veganism...realize that you're encountering in some form or another the same kind of passionate resistance that prompted some awfully big and widespread and deadly human conflicts. A lot of human animals have killed a lot of other human animals over exactly these kinds of thinkings...and they did this killing very much in recent times. This all didn't happen long ago and far away.
So, if you thought veganism was just about being "nice" to our sister/brother Earthlings....you might want to think again. It's rather more serious and possibly deadly (and hell if I know why) than that.