On 3 October 1944 American forces in the Pacific Ocean Areas received a directive to seize positions in the Ryukyu Islands (Nansei Shoto). Okinawa is the most important island of the Ryukyu Group, the threshold of the four main
islands of Japan. The decision to invade the Ryukyus signalized the readiness of the United States to penetrate the inner ring of Japanese defenses. For the enemy, failure on Okinawa meant that he must prepare to resist an early invasion of the homeland or surrender. Operation ICEBERG, as the plan for the Okinawa campaign was officially called, marked the entrance of the United States upon an advanced stage in the long execution of its strategy in the Pacific.