Hitler's declaration of war against the United States on 11 December 1941, in support of his Axis partner, the Empire of Japan, opened up the western Atlantic and American shipping to U-boats which had previously been ordered to avoid contact with the then-neutral Americans. The decision provided immediate tactical advantages against the unprepared Americans along the East Coast of the United States. The campaign became known as the "Second Happy Time" to U-boat crews, but not to Fliegerführer Atlantik.[82]