I hate to have to ask, as the question is not worth much to me, but it's so unpleasant to see a question closed for an ambiguous reason.
Commenters complained that it was "insufficiently notable", but I cannot find any stated criterion for notability.
Close voters called it "off-topic", as if I had violated the "What topics can I ask about here?" rules. However, the question is definitely is about a historical event, and as far as I can tell, doesn't fall in any of the prohibited categories.
So were all those people wrong, or is there in fact an unwritten notability rule, or is it written and I failed to find it?