The I Corps (First Corps) aka ("eye core"), nicknamed America's Corps, is a corps of the United States Army with headquarters in Fort Lewis, Washington. The I Corps serves under the United States Army Pacific (USARPAC). The current I Corps is a different organization from the I Corps of the Union Army during the American Civil War.
The corps was consolidated in the Army of Virginia under Major General John Pope, and fought in the Second Battle of Bull Run, as the Third Corps, Army of Virginia. Afterwards, its designation as I Corps was restored. Iit rejoined the Army of the Potomac and crossed the Potomac River into Maryland to fight in the Battle of Antietam, under Major General Joseph Hooker. There, the division of Pennsylvania Reserves, under Brigadier General George G. Meade, took heavy casualties through its hard fighting, and was withdrawn to replenish.
The command of the Army of the Potomac then changed to Major General Ambrose E. Burnside, and they moved southward to fight General Robert E. Lee's army at the Battle of Fredericksburg, where the corps was commanded by Major General John F. Reynolds, arguably the best Union corps commander in the Eastern Theater. He superbly led the corps through this battle, then through the Battle of Chancellorsville, with the army being led by General Hooker, who left the I Corps in reserve.
In its last major battle, the Battle of Gettysburg, General Reynolds was killed just as the first troops arrived on the field, and command was inherited by Major General Abner Doubleday. Although putting up a ferocious fight, the I Corps was overwhelmed by the Confederate Third Corps (A.P. Hill) and forced to retreat through the town of Gettysburg, taking up defensive positions on Cemetery Hill. The next day (July 2, 1863), the command was given to Major General John Newton, a division commander from the VI Corps, who led it through this battle, including the defense against Pickett's Charge, and through the Mine Run Campaign that fall. Afterwards, the I Corps was disbanded and its units were reorganized and absorbed into the rest of the army. The Civil War career of the I Corps was ended.
The corps was reactivated in 1898 for the Spanish-American War, under the leadership of Major General John R. Brooke, and elements landed on July 31, 1898, to take part in the Puerto Rico Campaign. It advanced to Guayama, where it fought a battle on August 5, but the armistice was signed before they could partake in a slated major attack. Both the I Corps from the 19th Century are unrelated to the current I Corps even though they carry the same name.
In February, the corps consisted of the 1st, 2d, 26th, 32d, 41st, and 42d Infantry Divisions. From February to July, 1918, the German Army launched four major offensives, attempting to secure victory before the full American force could be brought to bear. The final offensive, started in July 1918, was an attempt to cross the Marne, in the area of Chateau-Thierry, but the American lines (including I Corps) held, and the offensive was fought back.
Joseph T. Dickman, who had commanded 3rd Infantry Division during their famous stand at the Second Battle of the Marne, took command in October 1918, leading the unit during the Meuse-Argonne Offensive.
The I Corps shoulder sleeve insignia was approved by the Adjutant General, American Expeditionary Forces on December 3, 1918.
During World War II, the corps fought in the South West Pacific Area. Its initial operations were in Papua, reinforcing Australian forces, which had turned back Japanese attacks along the Kokoda Track. The Allied forces then took the offensive, against the Japanese beachheads at Buna and Gona.
Thereafter, I Corps engaged in the western part of Operation Cartwheel, the encircling and neutralization of the Japanese base at Rabaul in New Britain. After this operation was completed, I Corps took part in prolonged Allied mopping-up operations along the northern shores of New Guinea.
In by far the largest series of operations in the theater during the war, I Corps took part in the invasion of Luzon. It was still engaged on mopping up operations there at the end of the war.
After the end of hostilities, I Corps was assigned to Occupation Force Duty in Japan.
I Corps (Fort Lewis, WA)
Reconstituted 1944-06-27 in the Regular Army as Headquarters, I Corps; concurrently consolidated with Headquarters, I Corps (active) (See below), and consolidated unit designated as Headquarters, I Corps
Reorganized and redesignated 1967-12-01 as Headquarters and Headquarters Company, I Corps
Constituted 1927-08-15 in the Regular Army as Headquarters, XX Corps
Redesignated 1927-10-13 as Headquarters, I Corps
Redesignated 1941-01-01 as Headquarters, I Army Corps
Redesignated 1942-08-19 as Headquarters, I Corps