Well, yes and no. The fact is that during the "Phoney War", they had all the time to bring in more troops, so the border was well defended, except for a large hole in the Ardennes.
Guess where the Germans attacked?
Anyway, I'm started to wrry we're doing the same mistake the French did IRL: tanks scattered in infantry units, a defensive army that can easily be overrun by the German blitzkrieg machine, not nearly enough aviations...
I know a lot of this is fixed by the game (Like, we can't really produce tank divisions yet), but it's still frightening.
Along those lines, we should probably establish a mobile reserve one province behind the front lines. Motorized infantry divisions with attached armor, plus future armor divisions, so we can respond to the German attack wherever they hit us. It's the only counter for a blitzkreg, where the Germans will throw their entire might at one point on our lines.
I suggest that we hit Germany only after they commit their forces to the invasion of Poland, but that we make sure to attack Germany at that time.
Furthermore, if the Germans only hit our lines in one spot, we should advance on any part of the line that the Germans are weak.
Along those lines, I think we should focus most of our industry on building motorized divisions for our mobile reserve and offensive actions, with excess manpower being put into standard infantry divisions to hold the line.
I don't think we have access to sufficient bomber aircraft, so I suggest we build the best fighter planes that we can, to contest German air superiority. If we can't bomb them, the next best thing is not to get bombed by them.