The Battle of Saipan was a battle of the Pacific campaign of World War II, fought on the island of Saipan in the Mariana Islands from 15 June-9 July 1944. The Allied invasion fleet embarking the expeditionary forces left Pearl Harbor on 5 June 1944, the day before Operation Overlord in Europe was launched. The U.S. 2nd Marine Division, 4th Marine Division, and 27th Infantry Division, commanded by Lieutenant General Holland Smith, defeated the 43rd Division of the Imperial Japanese Army, commanded by Lieutenant General Yoshitsugu Saito.
Saipan, one of the 15 chain islands of the Mariana, was only approximately 1,300 mi (1,100 nmi; 2,100 km) away from home islands of Japan. It was a very important strategic point for the U.S. during the second world war in the pacific theater. It was the key position for the Americans to bring the war to Japanese home land.
After the battle, Saipan became an important base for further operations in the Marianas, and then for the invasion of the Philippines in October 1944. Bombers based at Saipan attacked the Philippines, the Ryukyu Islands and Japan. In response, Japanese aircraft attacked Saipan and Tinian on several occasions between November 1944 and January 1945. With the position secured, American army could also make advancement in the Philippines and also make direct contact with its Chinese ally.
For the Japanese, the defeat in the battle made the futility of the War in the Pacific all the more apparent. According to one Japanese admiral: "Our war was lost with the loss of Saipan" The famous American Marine Corps general said "it was the decisive battle of the Pacific offensive" and "it opened the way to the Japanese home islands." Four months later, the 100 B-29 bombers that took off from Saipan and attacked Tokyo, showed the decision to take Saipan was correct.
The loss of Saipan was a heavy blow to the Japanese ambition. A meeting of senior generals and admirals decided that a symbolic change of leadership should be made and Prime Minister Hideki Tōjō should step aside. In addition, the Emperor should move away from day-to-day affairs so as to avoid looking too directly involved with the now losing war, to distance himself from blame if the war were lost "shogun" Tōjō. Tōjō agreed and submitted his resignation. Emperor Hirohito—considering Tōjō the strongest war leader Japan had—resisted. Tōjō considered trying to shuffle the Cabinet but encountered too much hostility and gave up. On 18 July, Tōjō submitted again his resignation, this time unequivocally. His entire cabinet resigned with him