@serge i don't actually know what zionism is. My first introduction to the word is the protocols bullshit and I've kind of been wary of the term forever. Is zionism a real thing and, if so, what are its basic tenets. I've also been wary to ask about it because I don't know the motives of people on the internet very well. But why not now? No need to answer, I'm sure you're busy, I won't be offended.
A somewhat medium answer:
There's Zionism and there's a second aspect, which is simply "Jewish safety".
Israel holds 7 million Jews, or roughly half the world's Jews. Of those Jews, roughly 60% are, or are the descendants of the expulsion of the Jews from the MENA, an event where virtually all Jews were kicked out of every middle eastern country:
https://en.wikipedia.org/wiki/Jewish_exodus_from_the_Muslim_world
Of the others, many are Holocaust descendants, and many are from the former Soviet Union, where they also suffered antisemitism, as well as other Jewish refugees from around the world.
In other words, a nation largely composed of Jewish refugees, and it's illegal for Jews to own land, or in some cases, even be on Palestinian land, as well as Israel's neighbors, who have tried to destroy it more than once.
Anti-Zionism is the call for Israel's destruction, and thus the call for the death or forced expulsion half the world's Jews, most of which know no other nation.
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Because of that, many Jews (myself included) feel that calling for the death of half the world's Jews is an antisemitic act.
So there I've defined anti-Zionism, and not Zionism itself, so now I will define Zionism- largely through citing others.
Zionism is, at its core, the belief that Jews are unsafe in the diasporatic world and that due to the constant realized threat of antisemitism (as expressed by regular attacks on Jews), the best path to safety is to have a nation state that we can go to.
Everything else after that is up for interpretation, including the political structure of that nation, whether it should be on our ancestral homeland or not, the motivations on why it should exist (secular or religious) and where the borders of the nations lie.
In fact you are likely to find that as the old saying "Two Jews, three opinions" goes, it's even more for Zionism.
Now for resources to cite- I'll give you only a few.
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