Some months ago during this interminable election cycle, there was this brief thing where I guess somebody asked the Republican candidates if they'd kill baby Hitler, assuming they could time travel. All the candidates fell over themselves in the rush to appear tough by agreeing that yep, they would totally kill that baby. Then there were a few people I read on Twitter who asked why, if you could go back in time, you didn't just go back and try to make certain the Treaty of Versailles wasn't such a disaster, so that perhaps Germany isn't so bitter and resentful, making it a fertile ground for Hitler's message?
It sounds good, though I wonder how one would go about it. I feel simply appearing in the conference room is going to get you tackled, and dragged off to an asylum, where, assuming you keep insisting you're from the future, they ultimately lobotomize you and congratulate themselves on how much calmer you are, as you sit and drool while cockroaches crawl all over you. Meanwhile, someone among the assembled ends up with your time machine, and it's the beginning of Deadpool #26 (the volume prior to the current one), only it's Georges Clemenceau with a time machine instead of Hitler. It could turn out worse that way, you don't know. Clemenceau probably won't waste his time stealing a mech to go try and kill Nick Fury in the 1950s, so he might actually cause some damage.
Anyway, it seemed like it wasn't a bad idea, but then I read 1920: The Year of Six Presidents, and it made the whole thing seem futile. You'd have to convince Woodrow Wilson to fight against the plans to drop a massive war reparations bill on Germany, and as long as Britain and France could threaten to stay out of his League of Nations, he wasn't going to do that. Because nothing was more important to him than getting the League in place, on his terms and only on his terms. Which is a big part of why he failed to get Congress to ratify it, because he wouldn't agree to any of the changes they asked for. It was his way or the highway, because Wilson was convinced he was always right.
So rather than waste your energy bashing your head against the brick wall of Woodrow Wilson's sense of his own infallibility, a different approach. How hard would it be to avert the assassination of Archduke Ferdinand? The whole thing nearly didn't happen as it was, between people missing their marks, losing their nerve, using crappy equipment. If the driver is given the proper directions for the changed route, he doesn't stop right in front of Gavrilo Princip, and Franz and Sophie probably make it out of Sarajevo alive. Or even just step in front of Princip, tackle him, bump him as he goes to draw his pistol, something.
The more I thought about it, the more I wondered if it would do anything other than delay the inevitable. Britain and Germany had been jostling for position for awhile; would they have found some other pretext? And Serbia was hardly the only place in Europe where one or more ethnic groups were under the rule of another group, and not happy about it. But maybe a delay would be enough to shrink the scope of it. Alliances were shifting, treaties were signed, then altered. Maybe the circumstances that ultimately emerged wouldn't have sucked in most of Europe.