Arriving in Okinawa in August 1944, Ushijima took command of Thirty-Second Army. That unit had been established under direct control of the Imperial headquarters in March 1944 specifically for the purpose of defending the Ryukus Islands. By that time, the Thirty-Second Army numbered four divisions and five mixed brigades. However, its military potential was hugely diminished when the 9th Division, one of the elite units in the army, was relocated to Taiwan (Formosa) in December and not replaced on Okinawa. Ushijima did what he could to strengthen the island's defenses, but the loss of his best division forced him to change his strategy from pursuing a "fight to the finish" to instigating delaying tactics. The goal of this strategy was to prolong the battle against U.S. forces in order to forestall a landing in the main Japanese home islands as long as possible.
The Battle of Okinawa began on 26 March 1945 when the U.S. forces landed on the Kerama Islands. On 1 April, those forces went ashore on Okinawa proper. The landing was deceptively easy, as Ushijima had withdrawn the bulk of his forces to fight for the populous interior. The fighting continued into late June. With the battle lost, Ushijima committed ritual suicide on a cliff on 23 June (22 June, according to another account), leaving as his last orders: "Guard your own position, follow the orders of your superiors, and fight bravely to the last breath for your homeland." Ushijima had been promoted to the rank of general on 20 June, just prior to his death.
Gow, Ian. Okinawa: Gateway to Japan. Garden City, NY: Doubleday, 1985.; Komatsu, Shigero. Okinawa Ni Shisu: Dai-Sanjunigun Shireikan Ushijima Mitsuru No Shogai (Death in Okinawa: The life of the Thirty-Second Army Commander Mitsuru Ushijima). Tokyo: Kojinsha, 2001.; Ushijima Mitsuru Biography Publishing Group. Okinawa Gun Shireikan: Ushijima Mitsuru (Ushijima Mitsuru: Commander of the Okinawa Army). Kagoshima, Japan: Shunendo, 1980.