During the night of 7/8 December 1941, one hour before its attack on Pearl Harbor, the Empire of Japan began the invasion of Malaya. Four hours after the attack on Pearl Harbor, the Battle of Hong Kong began. Although the immediate British response was to order a number of units to be diverted to the Far East, none based in the Middle East were withdrawn for the moment. Since the convoy containing the 18th Infantry Division had only reached the Cape of Good Hope when Japan entered the war, it was diverted to the Far East on 9 December. Instead of reinforcing Operation Crusader as planned, the division was sent to India. Lionel Wigmore, the Australian historian of the Malayan campaign, wrote that the diversion indicated that "... the security of Singapore and maintenance of Indian Ocean communications were second in importance only to the security of the United Kingdom ..."