The Pacific war began on December 7, 1941 with bombing of Pearl harbor. This section of the war was mostly fought between the Allies and Japan. The major Allied participants involved in the Pacific war were the U.S., China, Britain, and Australia.
The U.S. used many strategic techniques in this war. One of these main techniques was the island-hopping campaign. This idea was to skip over heavily armed areas and concentrate on important islands that weren't well supplied. This technique slowly worked for the Allies.
Some of the major battles of WWII and the Pacific war were the Battle of Midway, Battle of Stalingrad, Battle of Britain, and the Invasion of Normandy a.k.a. D-Day. All of these battles played a key role in the outcome of WWII.
In the end, the dropping of two atomic bombs by the U.S. on Hiroshima (8/6/45) and Nagasaki (8/9/45) led to Japan's surrender from WWII.
Japan's official surrender from the war was on September 2, 1945.