Though I Corps was formally constituted in 1918 as part of the United States entry into the First World War, it traced its history to other entities known as I Corps that had existed in the US military before that. During the American Civil War, the Army of the Potomac, then under General McClellan, was reorganized into 4 corps by President Lincoln's directive in March 1862. One of these was designated as I US Corps. General McDowell was made the commander of the Corps. Troops of the Corps took part in the Battle of Manassas (Second Bull Run), and saw action at Antietam, at Fredericksburg, in the Chancellorsville Campaign, and at the decisive Battle of Gettysburg. Its troops served until, in a later reorganization of the Army of the Potomac, its depleted divisions were consolidated and transferred to V Corps and it was inactivated with the reduction of that Army to 3 Corps.
Another I Corps was activated in 1898 at Camp Thomas, Chickamauga, Georgia, immediately after the United States declared war on Spain. On 31 July 1898, under the command of Major General John R. Brooke, elements of the I US Corps were landed at Anayo to take part in the Campaign of Puerto Rico. The force advanced to Guayam, where it engaged the Spanish on 5 August 1898. An advance to Cayey followed in preparation for a major attack; however, before it was launched, the Armistice was consummated.
Following the declaration of a state of war with the Imperial German Government on 6 April 1917, and the entry of the United States into World War I, the Army was given the task of expanding the 165,000 men of the pre-war Regular army into a huge fighting force. Units of the American Expeditionary Force were shipped to France as they became available. With the build-up came the organization of these division-sized units into an American Army. Between 15 and 20 January 1918, Headquarters, I Army Corps was organized in the Regular Army in Neufchateau, France. Assisted by the French XXXII Corps, the headquarters was organized and trained. On 20 January 1918, Major General Hunter Liggett took command of the Corps, which then consisted of the 1st, 2nd, 26th, 41st, and 42nd Divisions, joined in February 1918 by the 32nd Division upon its arrival in France.
In the period from February to July 1918 the German Army launched a series of 4 major offensives intended to secure victory before the full resources and mobilization of the American nation could be brought to bear. The final offensive, begun on 14 July 1918, effected a crossing of the Marne in the vicinity of Chateau-Thierry, but the Allied lines held and a major enemy victory was averted. During this period, the I US Corps was active in the defense. From 4 July until 18 July 1918, it occupied 2 defensive sectors: Ile de France and Champagne-Marne.
With the defeat of these German offensives, I Army Corps received its first offensive mission and from 18 July until 6 August 1918 it participated in the Aisne-Marne Operation. The offensive resulted in the reduction of the more critical salients driven into Allied lines made by the German offensives. After a brief period in the defensive sectors of Champagne and Lorraine between 7 August and 11 September 1918, the Corps took part in the St. Mihiel attack. The offensive reduced the German salient there during the 4 days following its initiation on 12 September 1918. There the Corps experienced another period in the Lorraine defensive sector as preparation advanced for what was to be the final Allied offensive of the war. On 26 September 1918, Corps troops began the attack northward that opened the Meuse-Argonne Offensive. From that day until 10 November 1918, I Corps was constantly moving forward in the operation that broke the German will to resist. After the Armistice, the Corps undertook a training mission in France and was so engaged until its demobilization there on 25 March 1919.
During the period of its services during World War I, the Corps was awarded 7 battle honors for its engagements. At various times it had assigned to it the following American divisions: 1st, 2nd, 3nd, 4th, 5th, 6th, 26th, 28th, 32nd, 35th, 36th, 41st, 43nd, 77th, 78th, 80th, 82nd, 90th, 91st, and 92nd. In addition the 62nd, 167th, and 5th Cavalry Divisions of the French Army were also under its control at various times.
In the inter-war period, the Corps distinctive unit insignia and shoulder patch were adopted in 1922, when the Army designated the "Bulls-eye" insignia for Corps headquarters personnel. Also during this period, Headquarters, XX Corps was first constituted on 15 August 1927 in the Regular Army. It was redesignated on 13 October 1927 as Headquarters, I Corps.
As the signs of another World War became more distinct, the United States began the expansion of the Army in late 1940. I Corps was activated on 1 November 1940 at Columbia, South Carolina. It was redesignated on 1 January 1941 as Headquarters, I Army Corps. In the 9 following its activationm, the Corps supervised training and engaged in large-scale maneuvers. On 6 July 1942, Lieutenant General (then Major General) Robert L. Eichelberger took command of the Corps, which he was destined to lead through the majority of its service in the South Pacific. In the summer of 1942, the Corps was ordered to Australia. It was redesignated on 19 August 1942 as Headquarters, I Corps and closed into the area at Rockhampton, Australia on 17 October 1942. The Corps at that time consisted of the 41st Division, a small number of Corps troops, and the 32nd Division, of which elements were engaged in the desperate defense of British New Guinea.
Switching from the defensive and thereby ending the threat of an Australian invasion, the I Corps began the effort to push back the Japanese. With pitifully small forces, the 32nd Division and the 163rd Infantry Regiment of the 41st Division, the offensive was launched across the torturous, jungle-covered Owen Stanley Mountains of New Guinea. This force, later augmented by the Australian 7th Division (Reinforced), fought against a tenacious enemy under conditions of weather and terrain that truly tried the mettle of human determination. From 19 November 1942, when the offensive began, until the fall of Buna on the north coast of the island on 22 January 1943, I Corps pushed slowly forward in a campaign that was the first Allied victory against the Japanese Army and for which the Corps received the Distinguished Unit Citation. This victory marked the turn of the tide in the ground war against Japan.
After the campaign, the Corps returned to Rockhampton, Australia, where it was engaged in the training of the forces beginning to arrive in that area for the coming campaigns that were to terminate with the surrender of Japan. From February 1943 until March 1944, the Corps was preparing for its next assignment. That mission was the capture of Hollandia on the north coast of Dutch New Guinea. The units allocated to the Corps for the task were the 24th and 41st Infantry Divisions.
The Task Force established itself ashore after a successful amphibious assault on 19 April 1944 and began the reduction of the Japanese forces in that area for the subsequent establishment of air bases there. The battle was a vicious one. The jungles and swamps proved as much an enemy as the Japanese, and it was not until 6 June 1944 that the area was secured. The entire Japanese 18th Army was cut off from its bases by the leap-frogging strategy, of which the operation was a part. Following this campaign, the Corps directed the seizure of the island of Biak, which was secured by 24 June 1944, to complete the advances necessary for the subsequent invasion of the Philippine Islands.
On 27 June 1944, the I Corps that had served in the First World War was reconstituted in the Regular Army as Headquarters, I Corps. Its lineage and honors were concurrently consolidated with those of the active Headquarters, I Corps. The consolidated unit was designated as Headquarters, I Corps. On 20 August 1944, Major General Innis P. Swift succeeded General Echelberger as commander of the Corps upon the latter's assumption of command of the Eighth Army.
On 9 January 1945, I Corps successfully landed on the coast of the Lingayen Gulf in Northern Luzon, Philippine Islands, with the mission of establishing a base for future operations to the north and of denying the enemy northern access to the China Sea. In a sustained drive of 34 days, which covered 100 miles, the Corps crossed Central Luzon and thus separated the Japanese forces in the north from those in Southern Luzon. In so doing the Corps met and destroyed the armored forces that the enemy possessed. Following this accomplishment, the Corps turned northward and began the systematic reduction of the enemy positions in the wild, broken terrain on the approach to the Cagayan Valley. The Japanese had termed their defenses in this area "impenetrable," but Corps troops pushed over them. The breakthrough into the valley was followed by a swift exploitation that took the Corps to the north coast. This advance covered 200 miles in a little over 100 days. It eliminated effective enemy resistance in Northern Luzon.
Early in July 1945, under the direction of Sixth Army, I Corps began the planning intended to accomplish the invasion of Kyushu, the southernmost island of Japan. This planning was brought to an end on 14 August 1945 with the Japanese agreement to surrender under the provisions of the Potsdam Declaration. Plans were then drawn for the part that the Corps was to play in the movement to Japan and the subsequent occupation.
During the struggle in the Pacific, the Corps had participated in actions that stopped the Japanese juggernaut, pushed it back, and accomplished its complete defeat. At various times during the 2 and a half years in which it was in action, the following divisions were attached or assigned to it: 6th, 8th, 9th, 24th, 25th, 30th, 32nd, 33rd, 37th, 41st, 43rd, 77th, 98th, 2nd Marine, 7th Australian, and elements of the 11th Airborne. The Corps was awarded battle honors for its participation in 3 major campaigns: Papua, New Guinea, and Luzon.
On 19 September 1945, the Corps, with the assigned 33rd Division, sailed from Lingayen Gulf for Japan, landing on the Island of Honshu 3 weeks after the formal surrender, on 25 September 1945. Other units of the Corps followed and were assigned areas of responsibility. There followed 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 the means of warfare disposed of. The manifold duties of the occupation included conversion of industry, repatriation of Foreign Nationals, and supervision of the complex features of all phases of Japanese government, including economics, education, and industry.
From 15 November 1945 until 1 February 1948, the Corps was commanded by Major General Roscoe B. Woodruff. As the purely occupational mission was accomplished, troops of the Corps turned more to military training and field exercises designed to prepare them for combat. At this time, the Corps was comprised of the 24th and 25th Infantry Divisions, which were deployed on Kyushu and mid-Honshu respectively. Lieutenant General (then Major General) Joseph M. Swing assumed command of the Corps in February 1948, to be succeeded by Lieutenant General (then Major General) John B. Coulter in February 1949. On 28 March 1950, the Corps was formally inactivated in Japan.
The Corps had only a short period of inactivity, for with the entry of American troops into Korea it was again to be the "first." I Corps was reactivated at Fort Bragg, North Carolina on 2 August 1950 and advance elements of the headquarters took their place in the Pusan perimeter on 27 August 1950. The Headquarters, designated "Task Force Jackson," assumed control of the I Republic of Korea Corps, the 21st Regimental Combat Team, and the 3rd Battalion Combat Team of the 9th Infantry Regiment. On 12 September 1950, under command of Lieutenant General (then Major General) Frank W. Milburn, the Corps became operational.
Four days later the Corps participated in the attack that was to mark the changing tide of American fortunes. From the Pusan perimeter, Corps troops pushed northward against crumbling enemy opposition to establish contact with forces of the 7th Infantry Division driving southward from the beachhead established by the amphibious landings at Inchon. Major elements of the North Korean Army were destroyed and cut off in this aggressive penetration. The link-up was effected south of Suwon on 26 September 1950. The offensive was continued on to the north, past Seoul, and across the 38th Parallel on 1 October 1950. The momentum of the attack was maintained, and the race to the North Korean capitol, Pyongyang, ended on 19 October 1950 when elements of the 1st ROK and 1st Cavalry Divisions both entered the city.
The advance continued, but against increasing enemy resistance. On 25 October 1950, the first Chinese prisoners on the Eighth Army front were taken by Corps troops. By the end of October 1950, the city of Chongju, forty miles from the Yalu River border of North Korea, had been captured.
The complexion of the conflict suddenly changed on 27 November 1950 when massed Chinese attacks were launched against troops of the Corps. The overwhelming strength of these massed assaults forced the withdrawal of friendly forces. Valiant actions, unnumbered examples of personal intrepidity, and the skillful use of all forces and agencies of the Corps enabled the withdrawal to be effected. The Chinese attacked in the face of tremendous fires, seemingly indifferent to the number of their casualties. Friendly forces were able to remove much of their supplies. That which could not be removed was destroyed to preclude its use by the enemy.
Early in 1951, Seoul fell for the second time to the Communists. Following the establishment of defenses south of the capital city, the United Nations forces resumed the offensive. On 15 January 1951, the Corps was attacking to the north, Seoul was liberated again on 14 March 1951. The momentum of this attack carried the Corps over the 38th Parallel again.
As Corps troops approached the "Iron Triangle" formed by the cities of Chorwon, Kumhwa, and Pyonggang, a vital enemy supply and communication center, the Communist resistance increased. On 22 April 1951, the enemy took up the offensive. The attacks were again marked by masses of men thrown against Corps positions without regard for losses. These fanatical attacks were countered by the controlled withdrawal of friendly troops, according to prearranged plans, to previously prepared defensive positions. At each position the maximum casualties were inflicted upon the enemy and most advantageous use was made of firepower, then UN forces were moved to the next phase line prior to being over-run by the enemy.
This tactic proved successful and the momentum of the Communist offensive was absorbed. It was stopped short of Seoul and then its depleted forces were driven back by the United Nations counter-offensive that carried the Corps troops north of the Imjin River, to the positions that they were to occupy with slight alteration until the Armistice Agreement was reached more than 2 years later. The line was stabilized by 27 May 1951.
The peace talks began in July 1951, and action along the front was light for the remainder of the summer. Lieutenant General (then Major General) John W. O'Daniel assumed command of the Corps in July 1950. In October 1950, Operation "Commando" was launched with the objective of improving the Corps' defensive positions in the vicinity of Chorwon and of enabling UN forces to develop the rail line from Seoul to Chorwon to Kumwha. The missions of the offensive were achieved and the action for the remainder of the year continued light.
While the period from late 1951 until the Armistice was agreed upon and signed in July 1953 saw no battles ranging over large areas or great offensive moves, the whole period was one of intense military activity. With the relative stability of the fighting lines came the necessity for constructing semi-permanent fortifications. As the enemy's artillery potential rose, Corps troops were forced to increase the strength of these positions. This work was never completely done. Enemy fire reduced many bunkers that had to be rebuilt, thaws following cold weather weakened emplacements that had to be repaired, roads to grant access for tanks, and positions form which they could deliver direct fire into enemy positions had to be constructed.
In addition to this work was the ever-present necessity for aggressive patrolling to locate and destroy the enemy, to capture prisoners, and to screen friendly positions and activities from the Communists. These essential patrols were not to receive much-deserved publicity, but to the men who had to go on them, they represented combat of an intense and extremely dangerous nature.
The major offensive engagements of the period were generally limited objective attacks and raids by I Corps troops to keep the enemy off the terrain features close-in to the Main Line of Resistance, to hinder the enemy build-up, and to keep the troops in an aggressive attitude. The major defensive engagements were efforts to hold outposts located in front of the Corps defense positions and intended to protect the main positions. These efforts were made under severe handicaps, for these positions were frequently far out in "no man's land" and easier of access to the attacking enemy than to friendly reinforcement and counterattack.
In some cases they had to be evacuated in view of the cost of holding them against obvious enemy intentions to gain them at any cost. Under these circumstances the outposts could no longer be considered of tactical value. They had outlived their function of early warning and delaying enemy attacks on the Main Line of Resistance. Constant engagement in minor offensive or defensive missions, continual training of all units, and continuous alert-these characterized the activities after the late fall of 1951.
For 3 weeks, beginning in the last days of December 1951, the Communists unsuccessfully attempted to wrest positions near Tumae-ri from the determined 1st ROK Division. These efforts cost an estimated 7,000 enemy casualties. In June 1952, a 10-day attack against 45th Infantry Division outposts was likewise hurled back.
On 28 June 1952, Lieutenant General (then Major General) Paul W. Kendall assumed command of the Corps. The aggressive patrolling continued. The toll taken of the enemy attackers mounted steadily as proof to the enemy that attempts to penetrate the Corps' Main Line of Resistance were futile, but there seemed to be no consideration of the terrible cost.
September 1952 began with renewed enemy attacks against the outposts that protected the main line. Enemy attacks up to regimental size against garrisons of platoon and company strength were turned back without exception by the determined infantrymen of the Corps aided by the skill of their supporting tankers, artillery men, and service troops. Fighting teamwork of the highest order, sparked by individual and unit bravery and devotion to duty, was demonstrated to be superior to these fanatical attacks of the Communist hoards. The names of Bunker Hill, The Hook, Kelly, Old Baldy, Nori, and Pork Chop were synonymous with the gallantry of the men of I Corps. All along the front, the enemy was driven back with thousands of casualties.
On 23 January 1953, the first major action of the year was initiated with a raid by aggressive infantrymen of the 1st ROK Division against the enemy's Big Nori positions. The next months saw many such raids, which harassed the enemy, captured prisoners, and destroyed defensive works. Beginning in March 1953, the Communists were continually attacking the Corps outposts. In that month, troops on Old Baldy were withdrawn, on orders from Corps, after extracting a tremendous price in casualties from the enemy.
On 10 April 1953 Lieutenant General (then Major General) Bruce C. Clarke, who was to see the Corps through the remainder of its combat, assumed command from General Kendall. The fighting on the outposts continued. The 7th Infantry Division stopped wave after wave of the Chinese thrown against Pork Chop. Troops of the Turkish Brigade, attached to the 25th Infantry Division, defending the outposts named "Berlin," "Vegas," "Carson," and "Elko" fought fiercely in hand-to-hand combat with the enemy. They were ordered to evacuate all but the Berlin position at the end of May 1953. The Commonwealth Division ejected the Chinese after their assault on the Hook. The 1st ROK Division troops were ordered off the positions on Queen, Bak, and Hill 179 when heavy enemy assaults divested the positions of their tactical value. The closing days of the fighting saw the 7th Infantry Division withdrawn from Pork Chop and the 1st Marine Division ordered to evacuate the Berlin positions for the same reason.
The truce negotiations, which had been in progress for the preceding 2 years reached an end with the signing of the Armistice Agreement at 1000 on 27 July 1953. According to the terms of the agreement, it became effective 12 hours later and required the withdrawal of Corps troops 2,000 from the Demarcation Line running between the contending forces. The word was passed to the lowest echelons of the Corps and the firing ceased a few minutes before the historic hour. As the realization that the fighting was over spread among the front-line soldiers, they emerged slowly from their bunkers, not in an elated mood as might have been expected, but with the knowledge that another phase of the war had been reached and a sober understanding that the truce represented a temporary cease-fire requiring the continuation of the alert, ready-for-action attitude of the past.
The old positions were dismantled for the salvage of timbers, wire, sandbags, and other fortification materials needed on the new line. The troops moved back to the new Main Battle Position and began the hard work of preparing it to meet the threat of another Communist onslaught. The Demilitarized Zone, extending 2,000 meters on either side of the Demarcation Line, had to be marked and lanes through it cleared of mines and obstacles. Supply and service installations had to be displaced, roads to the new areas had to be constructed, and new plans had to be drawn. As these activities taper off, the training of replacements and the constant retraining of units assumed greater importance.
Major American units that served in I Corps in the Korean conflict were the 1st Cavalry, 1st Marine, 2nd Infantry, 3rd Infantry, 7th Infantry, 24th Infantry, 25th Infantry, and the 45th Infantry Divisions. Others of the United Nations having fought by the side of these American units were the 1 Commonwealth Division, composed of British, Canadian, Australian, New Zealand, and Indian troops; the Capital, 1st, 7th, and 9th Republic of Korea Infantry Divisions; and smaller units, integrated into American divisions, representing the Philippines, Belgium, Thailand, Greece, Turkey, the Netherlands, France, Colombia, and Ethiopia. Thus I Corps achieved its success as an Allied unit.
On 12 September 1953, I Corps completed 3 years of service in the Korean conflict. It saw the darkest days of the Pusan perimeter give way to the elation of a victorious drive almost to the Yalu. It absorbed the general offensive that marked the intervention of the Chinese Communist Forces into the conflict, and later pushed these forces out of South Korea. Following this drive it was again called upon to stanch the flood of attacking Chinese as they mounted their second and last major effort to drive the United Nations Forces from Korea. After a masterfully fought delaying action, I Corps troops again turned to the offensive and drove northward until halted by the Communist request for the initiation of the "truce talks." In the stabilized war that followed, Corps troops were ordered to hold their positions. This they did. The enemy was never able to penetrate the Corps' Main Line of Resistance despite his desperate efforts to do so.
I Corps remained in Korea after the Armistice. It was reorganized and redesignated on 1 December 1967 as Headquarters and Headquarters Company, I Corps. In 1971, I Corps was reduced to zero strength, remaining on the active rolls, but effectively inactivated. By 1982, the Third Republic of Korea Army had completely taken control of the area of responsibility formerly held by I Corps. It was to subsequently relocate to the United States, to be headquartered at Fort Lewis, Washington.
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