There were plenty of reasons for the Allies to suspect such an attack. Months beforehand, as Hitler began preparing for the offensive, Japanese representatives in Berlin had heard rumors of the preparations. Their messages were intercepted and decrypted, giving the Allies their first clue. Over the following months, the Germans moved troops, tanks, and planes west. They included powerful contingents of the SS, the politicized and vicious military elite of the Nazi war machine. Intercepted signals told the Allies those movements were happening, although not why. Aerial reconnaissance observations added to the evidence.
