Pacific · 15 Jun 1944 – 9 Jul 1944
Saipan and the Philippine Sea
U.S. forces captured Saipan after an amphibious campaign from 15 June to 9 July 1944; the Japanese fleet’s failed intervention in the Philippine Sea cost it heavily in aircraft and ships.
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The U.S. assault on Saipan began on 15 June 1944, after air raids, reconnaissance and naval bombardment. The 2nd and 4th Marine Divisions landed on the island’s southwest coast while the 27th Infantry Division remained in reserve. Japanese defenders had prepared concealed positions and artillery on the heights above the beaches. Resistance and difficult reef approaches slowed the landings, but the Marines established beachheads. Army troops began landing the following day. [Sources 1, 3, 4, 5](https://www.history.navy.mil/browse-by-topic/wars-conflicts-and-operations/world-war-ii/1944/saipan.html)
The landing brought a Japanese fleet intervention. On 19–20 June, the U.S. Fifth Fleet met the Imperial Japanese Navy’s First Mobile Fleet in the Battle of the Philippine Sea. U.S. forces inflicted severe losses on Japanese carrier aviation, and the Japanese fleet withdrew without stopping the Saipan operation. The naval battle did not end the fighting ashore: U.S. troops continued their advance while Japanese forces lost the prospect of effective air support or reinforcement by sea. [Sources 3, 7, 8](https://omniatlas.com/maps/asia-pacific/19440619/)
On Saipan, U.S. troops advanced north through rugged ground and fortified positions. The 27th Infantry Division joined the fighting after landing, while the Marine divisions continued their push. Japanese defenders, including forces of the 31st Army, contested the central heights and then withdrew toward the north of the island. The advance was slow and costly. Japanese resistance continued in caves and strongpoints even as U.S. forces narrowed the area still held by the defenders. [Sources 1, 3, 4, 5](https://en.wikipedia.org/wiki/Battle_of_Saipan_order_of_battle)
On 7 July, several thousand Japanese troops launched a large banzai attack on the Tanapag plain. The assault struck the U.S. Army’s 105th Infantry Regiment, part of the 27th Infantry Division, and overran two battalions before U.S. forces stopped it. The attack inflicted severe losses on both sides, but it did not restore Japanese control of the island. Organized resistance ended on 9 July, when U.S. forces declared Saipan secure. [Sources 2, 4, 8, 10](https://www.pbs.org/wgbh/americanexperience/features/pacific-war-pacific-1944-1945/)
The U.S. operation achieved its stated immediate objective: Saipan became an American-held base within range of the Japanese home islands. Casualty totals varied among the sources. A U.S. operational report recorded 3,143 killed, 13,208 wounded and 335 missing; Japanese losses in that report were 23,811 killed and 1,810 captured. Other sources gave higher Japanese death totals and civilian deaths ranging from 8,000 to 22,000. [Sources 1, 3, 4, 10](https://www.usmcu.edu/Portals/218/Saipan-Northern%20Troops%20and%20Landing%20Force%20%20Report,%20August%201944.PDF)