Why was Hitler not dettered by the British french guarantee to Poland?

Hitler was confident that the invasion of Poland would result in a short, victorious war for two important reasons. First, he was convinced that the deployment of the world's first armoured corps would swiftly defeat the Polish armed forces in a blitzkrieg offensive. Secondly, he judged the British and French prime-ministers, Neville Chamberlain and Edouard Daladier, to be weak, indecisive leaders who would opt for a peace settlement rather than war.