The Japanese attack on Pearl Harbor in December 1941 brought the U.S. into World War Two and also signaled the start of the long naval campaign in the Pacific. Japanese successes in early battles in South-East Asia, such as the invasion of Burma and Singapore, were mirrored by naval victories like the Battle of the Java Sea and attacks on Sydney Harbor in Australia. As a result, the Allies were firmly on the back foot.
Come the middle of 1942, in fact, Japanese forces controlled a huge area stretching from the Pacific to the Indian Ocean. Their naval resources were extremely overstretched, however. And significantly, June 1942 saw a major engagement between Japanese and American air and naval forces at the Battle of Midway. The U.S. emerged the victors of this fierce battle, and historians view it as a turning point in the fight for control of the Pacific.
The next major engagement in the Pacific came at Guadalcanal in the Solomon Islands. In August 1942 some 16,000 troops, mainly U.S. Marines, landed on Guadalcanal, capturing the Japanese airfield there. The intense battle continued for six months, before the superiority of American industrial capacity and manpower resources eventually began to tell.