Jean Jaurès was a French socialist very active in 1914 to try to defuse the possibility of war between France and Germany. He was the main artisan between the Second International's plan to make a simultaneous general strike in Germany and France if war was declared. He was killed on 29th of July 1914. War was declared 5 days later. Without him, the plan did not go forward.
Had he not died, some suggest that it would just have handicapped France's chances (somehow assuming that Germany would suppress strikes quicker) and some other suggest that it could have defused the whole situation. Does /r/askhistorians/ has any light to shed on this?
It seems highly unlikely. Public opinion was virulently pro-war, with the press dominated by pro-Russian and anti-German sentiment in the crucial weeks leading up to his assassination. This national blood-lust killed Jaures as much as the miserable whack job who shot him. The SFIO was a deeply divided organisation as Guesde and Jaures differed greatly in their approach to democracy and republicanism and its relation to the class struggle. This atomisation of the Left also finds its roots in the deeply regional nature of French politics- even in 1914, France remained a broadly rural society lacking a substitutional national proletariat on the level of Britain. The SFIO also lacked the full support of the CGT (the most radical Trade Union organisation), which was broadly anarchist in nature. In terms of organisation, then, it would have been difficult to stage a general strike in France, let alone on an international level. One of the more tragic truths of the 20th century was that it was only in the crucible of horrific war that emancipatory movements seemed to properly take off. I hope that goes some way towards answering your question. If you're interested in Jaures, I'd recommend Max Gallo's biography.