Would it be even theoretically possible for a time traveler to prevent WWI?

That is, assuming the existence of time travel, and handwaving any causal-paradox problems. If you could go to Sarajevo on June 28, 1914, and grab Gavrilo Princip’s gun hand just as he’s about to shoot Archduke Franz Ferdinand, would that be enough to prevent WWI and all its consequences (the Bolshevik Revolution in Russia, the reactive rise of fascism, etc.)? Or was inevitable that the two alliance-camps into which Europe was then divided would find something, sooner or later, over which to go to war?

Of course it depends entirely on the nature of reality. If there are multiple universes, then such an action would result in a different world as a result of you preventing WWI.

If the nature of reality is such that this would not occur (ie, no parallel universes), then I do not think that you could prevent this from occurring.

Actually I think I misinterpreted the question.

Your question is about inevitability, not necessarily time.

My bad.

I think it was inevitable.

Germany was becoming an industrial power, and for whatever reason felt it had to displace some other power in order to take it’s rightful place on the world stage. (As opposed to taking their place alongside the others.)

Russia, Austria-Hugary, and the Ottoman Empire are/were seen as in their decline, and one of the reasons the Austrians pushed for war with Serbia was to try and halt this slide.

Britain wanted to maintain the status quo, and did not any one continental power to become too powerful. (It’s bad for buisness.)

I think the war was inevitable, but the outcome would definitely been different. Countries that were stockpiling weapons and otherwise preparing for the conflict to come would have come out better by the delay, I think.

Which countries were those?

No.

Princip would have been able to quantum jump into a parallel universe and start WWI over there.

It’s all explained here (one of the Google links accompanying this thread).

To, um, more directly answer the OP’s question, it would have made more sense to time travel back to when the plan employing Princip was being hatched, and to shoot the Serbian nationalist leader(s) feeding money into the Black Hand to commit terrorism against Austria.

Of course, in such a universe, time-travel (as we use the term) wouldn’t be possible at all, since merely existing, walking around, absorbing photons, etc. would “alter” the path of causality.

My opinion is that WWI could have been postponed. In another thread, it was noted that Europe almost went to war in several earlier crises. Germany was rattling sabers pretty loudly during the Boer War. There were other close calls.

1914 could have been one of them, and deliberate, intelligent efforts by someone with a “miraculous” or otherwise contra-historical source of knowledge might have done the trick.

Simply preventing the assassination in Sarajevo is relatively easy; any single chap could do it, given full knowledge of the events as they happened.

(For instance, just fire a pistol at the car’s tires, early in the trip, forcing a cancellation!)

Does the Spanish Flu still hit in 1918? I could picture the various nations using their military stockpiles not to wage war, but to “iron curtain” their borders, strangling off travel and trade and any thoughts of going invading.

Actually I did go back in time and grab Gavrilo Princip’s hand. Turns out he only wanted to kill the guy carrying the Archduke’s briefcase. He had knocked up Gavrilo’s sister, and then dumped her. I didn’t realize that, and the result of grabbing his hand was the Archduke and Duchess getting shot instead. Oops! Boy was my face red. Luckily the time machine brought me back, right out of the hands of some cops dressed like a marching band. And once again my attempt to alter the past had failed.

“The Law of Conservation of Reality.” (per Fritz Leiber.)

The past strongly resists being changed…

“All You Zombies,” by Heinlein, is one of the grimmest examples. “Rumfuddle” by Jack Vance is much more fun!

I think World War I in the sense of a general war of the great European wars was inevitable. However a different war can prevent the rise of a Communist Russia and Nazi Germany so I would try to as a time-traveller tried to mess with history as much as possible.

“So, did you hear that our Franz Ferdinand was shot?”

“Who did it? I bet it was a Serb. That would be great, since then we could go to war with Serbia.”

“No, it wasn’t a Serb.”

Then it was another subject race, put up to the job by the Serbs, so we can have a war with Serbia."

“No, it was some oddball from America, wearing strange pants that only come to the knees, but with huge pockets; something called a ‘Hawaiian’ shirt, and a billed cap with a low, domed crown.”

“Well, what’s the use of a war with Hawaii then?”

It seems likely that the conditions of the war helped spread the disease and/or helped intensify the lethality of the virus.

Reading historian Barbara Tuchman’s The Proud Tower, about the years leading up to the eve of WW1, one gets the impression that all the major powers were spoiling for a fight, and the system of alliances which pre-war helped maintain a sense of security guaranteed that if war did break out it would be a coalition war. Serbia was fighting for it’s very existence against being swallowed up by Austria-Hungary and could only survive with Russian backing. Germany and Austria-Hungary were natural allies against Russia. France couldn’t face Germany alone and Russia was Germany’s other main enemy so an anti-German alliance between France and Russia was obvious. And Britain had more reasons to be against Germany than France (although Anglo-French detente wasn’t inevitable).

It didn’t help that the realities of warfare at the time made the decision to go to war hair-trigger: the railroad-based requirement to commit or not commit to mobilization; the knowledge that every day you fell behind your enemy in mobilizing meant a day they could advance practically unopposed; and the fear that an unopposed enemy army could overrun you and that speed was essential meant that all the major powers were going by Napoleon’s maxim “he who hesitates is lost”.

In hindsight the only way to defuse the powder keg would be a Serbian/Austria-Hungarian/Russian accord whereby Serbia would be guaranteed of it’s independence conditional on not abetting Serbian-nationalist rebellion within Austria-Hungary, with Russia mediating and guaranteeing the accord. Russia itself was a polyglot empire with a huge potential for internal rebellion and if wiser heads had prevailed would have seen the sense of not setting the precedent of tolerating nationalist terrorism. Instead, Serbia winked at terrorism, Austria-Hungary demanded terms just short of annexation, and Russia said “you leave my little brother alone!” The problem was that no one could back down and no could could abandon their allies.