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 U.S. Army Pacific Command (USARPAC).
I Corps of the Australian Army was the main frontline corps of the army during World War II. Various Australian and other Allied divisions came under its control at various times. In 1940-42, the corps was based in the Mediterranean Theatre.
The Polish 1st Corps was a tactical unit of the Polish Army during World War II. Contrary to its name, in reality it never reached corps strength and was not used as a tactical unit until after the war, when it took part in occupation of Germany as part of the Allied forces stationed around the port of Wilhelmshaven. Prior to that date both of its main units fought separately and were listed together mostly for logistical reasons.