There are numerous Internet sites covering World War II in the Pacific.
Wikipedia has articles on all major, as well as many minor, engagements.
The U.S. Army Center of Military History has links to published material including the Reports of General MacArthur and a description of the Luzon campaign from the Japanese perspective.
The Hyperwar site has links to many detailed histories including those under The War in the Pacific heading where you can find an online version of the excellent, detailed books histories by Robert Ross Smith listed above.
A map of the Pacific Theater in 1942.
And last, but definitely not least, visit the home of the 6th Infantry organization for stories, photos and more, sponsored by the 6th Infantry veterans’ organization.