The Great War and its conclusion, WW11, were unlike anything before or since. There would still have been conflict but nowhere near that murderous scale.
True, but I wouldn't blame Mohammed entirely, more the people who have twisted the information he relayed, for their own ends. Perhaps he should never have gone into that cave in the mountains....
I'd not have Hitler, if I had a choice of removing an event.
I'd make sure that Captain Smith on the Titanic in April 1912 decided to forget about the Blue Riband until next time, and just slowed down to make sure that he got to New York this time. A staggering number of really important and potentially influential people died that night.