So let's recap. Great Britain and France have been watching Hitler prance around Europe demanding this and that, and have so far indulged his whims, though with an increasing degree of wariness. When he directly contravenes the Munich Agreement, they take a firm stance, and say "Right! The next country you invade, you will be VERY SORRY you did it!". He ignores them entirely and invades Poland. The scene is set for an epic battle between freedom and hate...
...and then everybody stops for tea and biscuits for no apparent reason. You're at war with him, he's distracted in Poland, why are you not kicking his sorry arse all the way back to Brunau-am-Inn? Seriously, Britain and France, what the hell?
Very well then. Let's have no more of this nonsense, and devise a way to start WWII right off the bat.