Board Thread:General Discussion/@comment-1982633-20141114080928/@comment-3428312-20141126192147

IIRC during the 1917 Mutinies, there was a division of the mutineers that boarded a train with the intention of going to Paris. Unfortunately for them, the French Government got wind of it just in time to deploy some Algerians colonial troops who intercepted and badly shot the train up which forced the mutineers to surrender.

So there's a viable POD for your purposes. I'm not for sure if these men had any socialist radicalization among them or if they could even be successful in toppling the French Government, but the chaos they would inevitable create could birth a situation like that in Russia that would lead to a Communist France eventually.