Who's "us"? Hast du eine Maus in der Tasche?
Most Germans I know have a better grasp of twentieth century history than you appear to. I wouldn't relay too heavily on the nonsense that extreme rightists in the US promote as 'German history', regardless of how comforting it might be to you.
Yes, Britian and France had sworn to defend Poland, and both of us sent ultimatums to Hitler demanding that he withdraw from Poland. Hitler ignored them all, which left us no choice.