The , codenamed
Operation Iceberg, was a series of battles fought in the
Ryukyu Islands, centered on the island of
Okinawa, and included the largest
amphibious assault in the
Pacific War during
World War II, the 1 April 1945 invasion of the island of Okinawa itself. The 82-day-long battle lasted from 1 April until 22 June 1945. After a long campaign of
island hopping, the Allies were approaching Japan, and planned to use Okinawa, a large island only away from mainland Japan, as a
base for air operations on the planned invasion of the Japanese mainland (coded
Operation Downfall). Four divisions of the
U.S. 10th Army (the
7th,
27th,
77th, and
96th) and two Marine Divisions (the
1st and
6th) fought on the island. Their invasion was supported by naval, amphibious, and tactical air forces.