In the months leading up to the invasion, the Allies worked at military deception. German coastal defences were stretched thin in 1944. Once Normandy had been chosen as the site of the invasion, it was decided to attempt to trick the Germans into thinking it was a fake invasion and that the true invasion was to be elsewhere. This was called Operation Bodyguard. In the weeks leading up to the invasion, the Allies tried to make the Germans think that the main invasion would take place at the Pas de Calais and in Norway. The deception was an industry in itself. It included dummy messages, dummy tanks in places near Dover and the south coast of England, using double agents to spread false information, dummy radio messages, and so on.