You also start with a larger army than Germany in 1936 (they catch up and surpass you pretty quick though), so if you push them over the remilatirization of the Rhineland you can beat them then and there. I don't know about earlier titles though.
The key is to build forts (while making sure you have enough guns), then wait years for an opening. I've played Democratic France more than once and won in HOI4 (you can also have a very simple and easy time by going Communist and joining the Comintern, but I assume you weren't asking about those kind of tactics).
