Why, when Hitler had sent in only three lightly armed battalions, with orders to withdraw immediately if they met resistance, did France, with the most powerful army in the world, not march in, send the Germans scurrying back over the Rhine bridges, and restation French troops on the river? Decisive action, warranted by Versailles and Locarno, to which Britain was signatory and which she would have had to back up, might have prevented World War II.