When did Hitler begin to rebuild Germany's army?

He started doing it in secret in 1933 because after WWI, Germany had military restrictions placed on it by the Allies and The Treaty of Versailles. In 1935 though, Hitler felt as if he was powerful enough to declare to the world that he had greatly (and illegally) expanded German's military to include 300,000 men in the army (was supposed to be limited to 100,000) and 2,500 planes in his air force (They were supposed to be banned from having an air force at all!).

Hitler then announced that he would increase the size of the army beyond that even, to 550,000 men and that military service would be made mandatory.