X Corps (United States)

X Corps was a corps of the United States Army in World War II and the Korean War.

World War II
The X Corps was activated in May 1942 at Sherman, Texas. It embarked for the Pacific Theater in July 1944 after two changes of station and participation in maneuvers in Louisiana and at the California-Arizona maneuver area.

X Corps took part in the following campaigns: New Guinea, Leyte, and Southern Philippines.

As part of the Sixth Army, X Corps took part in the Philippines campaign of 1944–45, beginning with the invasion of Leyte. For its involvement, the X Corps received the Philippine Presidential Unit Citation with a streamer embroidered 17 October 1944 – 4 July 1945.

X Corps became inactive in 1946.

Operation CHROMITE
The Battle of Inchon

During the Korean War, it took part in Operation Chromite, the landings at Inchon, where it had the 1st Marine Division, the 7th Infantry Division and other US Army units under its command. The embryonic planning group for CHROMITE originally was known to insiders as "Force X" and the entire scheme was cloaked in absolute secrecy; to outsiders the small planning staff was known only as the Special Planning Staff of general headquarters, Far East Command. As the organization grew, due to bureaucratic entanglements supply orders were rejected because "Force X" was not referenced as a proper organization anywhere in Army manuals. General of the Army Douglas MacArthur (Supreme Commander Allied Powers) asked his Chief of Staff, Major General Ned Almond, to suggest a new name. Force X's Roman numeral ten reminded Almond of a corps which had fought under MacArthur in the last war—"why not call it the X Corps?" he asked. MacArthur was delighted and approved of the name. General Almond was subsequently chosen by MacArthur as X Corps' new commander.

The Marines first captured an island offshore of Inchon as a prelude to the assault and at the next tide, the main attack went in. Despite the noise of the attack on the offshore island, it completely surprised the North Korean forces. The Marines then moved on to the capital city of Seoul; in heavy fighting they eventually drove out the North Korean defenders. The US Army's 7th Infantry Division, which had landed later at Inchon, engaged the enemy on the outskirts of Seoul, destroying an armored regiment.

Inchon had a very large tidal range, and was thus very risky to use as a landing site. Nonetheless, the landing proved to be an enormous success. It is by far the largest amphibious assault to have taken place since World War II, and one of the boldest.

Operation TAILBOARD
The X Corps' planned amphibious landing on the east coast of North Korea is amended by UNC OPORD No. 4 culminating in a withdrawal to the sea. The Battle of Chosin Reservoir

After the landing at Inchon, X Corps attacked up the Korean peninsula on the left flank of Eighth Army. However, it was withdrawn to prepare for another amphibious assault, this time at Wonsan on the eastern coast. This action proved to be a mistake on two counts. First, forces of the Eighth Army moving by land reached Wonsan before the assault went in. Second, it proved to be too far for UN forces to go. After an administrative landing at Wonsan, X Corps, now including the US 3d Infantry Division, advanced inland northwest towards the Yalu River with the First Republic of Korea (I ROK) Corps made up of two ROK Divisions in the far north or right flank. The US 7th Infantry Division was in the center and the US 1st Marine Division (MARDIV) on the southern or left flank of the X Corps attack. 3d Infantry Division was initially in reserve. As elements of the I ROK Corps and 7th Infantry Division closed on the Manchurian border, the 1st Marine Division hesitated and became bogged down in the vicinity of the Chosin Reservoir (Changjin Ho). The Chinese Communist Forces choose this moment to intervene en masse in the war. They crossed the Yalu into northern Korea and engaged 8th Army and X Corps across their frontages. The Marines were on both left and right sides of the Changjin reservoir. Regimental Combat Team 31 (RCT31 AKA Task Force Faith) of the Army's 7th Infantry Division replaced the 5th Marine Regiment on the east side of the reservoir in a piecemeal fashion with only two of its maneuver battalions in place before heavy engagement with the enemy commenced. X Corps was strung out along many miles in sub-freezing temperatures with the ROK troops and the 7th Infantry Division to the north in contact with enemy forces. Regimental Combat Team 31 was too far from its parent Division for support and without organic tank support and its third maneuver element; it was decimated by the onslaught of the Chinese. The 1st MARDIV fared better and with remnants of RCT31, Army Engineers and X Corps support personnel, began its move to the sea moving through elements of the 3rd Infantry Division (Task Force Dog from the 7th Infantry Regiment, and a reinforced battalion of the 65th Infantry Regiment ) who provided flank and rear guard cover for the withdrawing units. The 7th Infantry Division in the center and the I ROK Corps on the right flank also began withdrawing to the Hungnam beachhead. The Marines withdrew through the 3d Infantry Division with intermittent contact with Chinese forces up to Sudong. The extreme temperatures during this period caused the majority of the casualties for X Corps. The Marines managed to reach the safety of Hungnam first, where the 3rd and 7th Infantry Divisions and I ROK Corps provided perimeter defense. The Marines were evacuated by the middle of December, followed by the 7th Infantry Division, I ROK Corps and the last of the X Corps' elements. The 3d Infantry Division was last to leave the beach and evacuated on 24 December 1950.

For intrepid service during the Battle of the Chosin Reservoir with Chinese Communist Forces: U.S. Army Lieutenant Colonel Don C. Faith, Jr., having assumed command of Regimental Combat Team 31 7th Infantry Division, for actions during the period 27 November through 1 December 1950, U.S. Army Lieutenant Colonel John U. D. Page, of the X Corps Artillery, having distinguished himself in action during the period of 29 November to 10 December 1950 and U.S. Marine Corps Staff Sergeant William G. Windrich, Company I, 3d Battalion, 5th Marines, 1 December 1950 were posthumously awarded the Medal of Honor.

Receiving the Medal of Honor in person: U.S. Marine Corps Lieutenant Colonel Ray Davis, in command of the 1st Battalion 7th Marines for his actions 1 through 4 December 1950, U.S. Marine Corps Captain William E. Barber, in command of Fox Company 2nd Battalion 7th Marines, for his actions during the period 28 November through 2 December 1950, U.S. Marine Corps Staff Sergeant Robert Kennemore, Company E, 2d Battalion, 7th Marines, for his actions during the period 27 and 28 November 1950, and U.S. Marine Corps Private First Class Hector A. Cafferata, Jr., Company F, 2d Battalion, 7th Marines, for his actions on 28 November 1950.

Later actions
After the withdrawal from the northeast coast, and once its units had been reconstituted, X Corps went into the line, and remained there for the rest of the war. It is widely contended that X Corps remained outside of the direct command of Eighth Army too long. X Corps reporting directly to the Supreme Commander had been necessary for the Inchon landings and still defensible for the Wonsan attack. However, after it entered the main line, conventional military doctrine indicated that it should have been placed immediately under the command of Eighth Army. General Douglas MacArthur, the commander of the United States forces, was accused of favoritism towards Edward Almond, the controversial commander of X Corps, who was dual-hatted as the commander of X Corps and MacArthur's Chief of Staff and his personal friend.

After X Corps was placed under the command of Eighth Army, it performed with powerful strength for the rest of the war.

Post-Korean War
In the years following the Korean War, X Corps served as a regional headquarters, having administrative, logistical, and training responsibility for both active and Army Reserve units in the northwestern portion of the Continental United States.

X Corps was deactivated on 31 March 1968, as part of the compromise between U.S. Secretary of Defense Robert S. McNamara who wanted to merge the Army Reserve into the Army National Guard, and the United States Congress who wanted to maintain the Army Reserve as it then existed. Under the compromise plan, all of the combat divisions and most separate combat brigades of the Army Reserve were deactivated with a corresponding increase in the National Guard; at the same time, non-divisional combat support and combat service support units were reallocated in the Army Reserve. The fourteen area corps were deactivated; in their place, eighteen army reserve commands ("ARCOMs") were established. Each ARCOM was, in turn, assigned to one of five continental U.S. armies ("CONUSAs") under Continental Army Command ("CONARC"). The bulk of X Corps' Army Reserve units were assigned to the 124th Army Reserve Command.