Mouwembleem 9th Corps (Sleeve patch 9th Corps)

IX Corps was a corps of the United States Army. For most of its operational history, IX Corps was headquartered in or around Japan and subordinate to US Army commands in the Far East.

Created following World War I, the corps was not activated for use until just before World War II almost 20 years later. The corps spent most of World War II in charge of defenses on the West Coast of the United States, before moving to Hawaii and Leyte to plan and organize operations for US forces advancing across the Pacific. Following the end of the war, IX Corps participated in the occupation of mainland Japan.

The corps headquarters was finally activated on 24 October 1940 at Fort Lewis, Washington as part of a large buildup of the US Army in response to conflicts around the world. It immediately began training of combat units in preparation for deployment. One year later, IX Corps took command of the Camp Murray staging area in Washington, responsible for training Army National Guard forces in addition to its responsibilities training active duty and reserve units.

Following the Japanese attack on Pearl Harbor in late 1941, IX Corps was assigned to defensive duties on the West Coast of the United States, specifically the central and northern regions of the coast. The corps oversaw defenses on the West Coast for the majority of the war, but in 1944 it was moved to Fort McPherson, Georgia in preparation for deployment overseas.

Planning

The corps trained at Fort McPherson in preparation for deployment to the Pacific Theater of Operations. On 25 September 1944, the corps closed headquarters at Fort McPherson and moved to Hawaii. When it arrived in Hawaii, IX Corps was put under the command of the Tenth United States Army. Under the Tenth Army, IX Corps was assigned two missions. In 1944, it was primarily concerned with formulating plans for an invasion of the coastal regions of Japanese-held China. Later in 1944 and early 1945, it was placed in charge of preparing the rest of the Tenth Army for movement to Okinawa in preparation for an invasion of the island, which was launched in April 1945.

When General of the Army Douglas MacArthur took overall command of Pacific Forces, IX Corps was moved to Leyte in the Philippine Islands and was assigned to the Sixth United States Army in July 1945. In Leyte, the corps was tasked with the planning of Operation Downfall, the invasion of mainland Japan, specifically the island of Kyushu. It was also tasked with planning occupation once Japan surrendered. IX Corps was assigned as one of four Corps under the command of the Sixth Army, with a strength of 14 divisions. With the 77th Infantry Division, the 81st Infantry Division and 98th Infantry Division, a force of 79,000 men, IX Corps would serve as the Sixth Army's reserve force during the initial invasion. Before the assault could be launched, Japan surrendered in August 1945, following the use of nuclear weapons on Hiroshima and Nagasaki.

Occupation

Following the surrender, IX Corps was assigned command of occupation forces on the northern island of Hokkaidō. IX Corps transferred its headquarters in October 1945 to Sapporo for occupation duties. The next few years were a period during which the terms of the surrender were supervised and enforced; Japanese military installations and material were seized, troops were disarmed and discharged, and weapons of warfare disposed of. The duties of the occupation force included conversion of industry, repatriation of foreign nationals, and supervision of the complex features of all phases of Japanese government, economics, education, and industry.

As the occupation duties were accomplished, the occupation force continued to downsize as more troops returned home and their units were deactivated. By 1950, the Sixth Army had left Japan, and the occupation force was reduced to the Eighth United States Army commanding two corps and four under-strength divisions; the I Corps, commanding the 24th Infantry Division and 25th Infantry Division, and the IX Corps, commanding the 1st Cavalry Division and the7th Infantry Division. IX Corps had been moved to Sendai as the occupation forces shifted as a result of the downsizing. As part of further downsizing, IX Corps was deactivated on 28 March 1950, and its command responsibilities were consolidated with other units