U.S. Marines and Army forces breached the outer ring of the Japanese Pacific territories, which gave the U.S. forces a major staging area for the dive in the Central Pacific Isles.
The British and American strategies in the CBI theater slogged through difficult terrain, weather issues, and disease in order to stop the Japanese drive into India.
The Marianas Campaign was designed to take the key islands of Saipan, Tinian, and Guam, providing bases for B-29 bombers to reach the Japanese Home Islands.
Admiral Nimitz ordered the invasion of Iwo Jima in the largest Marine force ever concentrated for a single battle in the history of the world.
Okinawa was key island and had to be taken as it would be the springboard form an invasion of the Japanese Home Islands. This was the final great battle of World War II.