It is uncertain when Wilhelm turned against Nazis, but according to Snyder by start of 1942 he possibly already was spying for some intelligence services, possibly the British SIS which financed and supported resistance movements throughout whole Europe. Eventually he became a spy for the French resistance against the Nazis and then the Soviet Union. In 1944 he became acquainted with some French national Paul Maas who in some documents mentioned as Masse, but possible the name is pseudonym in any case. Germans deported Maas from France to Vienna and forced him to work at the military aviation factory, creating blueprints. Paul had connections whether with British intelligence or French resistance movement or possibly both handing over to his curators copies of factory blueprints for parts. Wilhelm accepted the Paul's offer to fight the occupants together. Thanks to his acquaintances with German officers, Wilhelm became a source of valuable information. From him the Frenchman was receiving information about the movement of Nazi troops as well as German war industry in Austria. Later at interrogations Habsburg said that he was driven exclusively by the hatred to Nazism.