Although the amendment to the Tripartite Pact was not yet in force, Hitler chose to declare war on the United States and ordered the "Reichstag", along with Italy, to do so on 11 December 1941, three days after the United States' declaration of war on the Empire of Japan. Roosevelt's "shoot on sight" order had effectively declared naval war on Germany and Italy in September 1941, and Germany had learned of Rainbow Five in early December. Hitler could no longer ignore the amount of economic and military aid the US was giving Britain and the USSR. Hitler's hopes that, despite the previous rejections, Japan would reciprocally attack the Soviet Union, were not realized, as Japan stuck to its Nanshin strategy of going south, not north, and would continue to maintain an uneasy peace with the Soviet Union. Nevertheless, Germany's declaration of war further solidified German–Japanese relations and showed Germany's solidarity with Japan, which was now encouraged to cooperate against the British. To some degree, Japan's actions in South-East Asia and the Pacific in the months after Pearl Harbor, including the sinking of HMS "Prince of Wales" and HMS "Repulse", the occupation of the Crown Colonies of Singapore, Hong Kong, and British Burma, and the raids in the Indian Ocean as well as on Australia, were a tremendous blow to the United Kingdom's war effort and preoccupied the Allies, shifting British (including Australian) and American assets away from the Battle of the Atlantic and the North African Campaign against Germany to Asia and the Pacific against Japan. In this context, sizeable forces of the British Empire were withdrawn from North Africa to the Pacific theatre with their replacements being only relatively inexperienced and thinly spread divisions. Taking advantage of this situation, Erwin Rommel's Afrika Korps successfully attacked only six weeks after Pearl Harbor, eventually pushing the allied lines as far east as El Alamein.