The motto of IV Army Corps - Greece - is 'Gordian Knot'.
IV Corps - Pakistan - was created in 1965.
IV SS Panzer Corps was created in 1943.
IV Corps - United States - was created in 1939.
IV Corps - United Kingdom - was created in 1940.
Officially called Military Regions I, II, III, and IV; aka I Corps, II Corps, III Corps, and IV Corps. I Corps was near the DMZ, II Corps was the Highlands, III Corps Saigon AO (Area of Operations), and IV Corps was the Mekong Delta.
None. The 34th "Red Bull" Infantry Division served in North Africa and all during the Italian Campaign. They were first attached to the II Corps and later to the IV and maybe VI Corps. The V Corps took part in the D-Day landings at Normandy. They were part of the 1st Army for awhile, then the 3rd Army and finally the 7th Army. However the 5th Army did serve in Italy and the 34th Infantry Division served under its command.
Not a conventional US Army division. But the US Army's 75th Rangers were in South Vietnam. The 75th had "Ranger" companies strung out in each MR (Military Region I, II, III, and IV/also called I Corps, II Corps, etc.). For example P company (called Papa 75th Rangers) were in I Corps. Kilo 75th (K company) may have been in either II or III Corps, etc.
Vietnam was divided into four different areas with I Corp in the North and IV Corps in the South of the South of the country.
Iris IV was created in 1990.
Eulogy IV was created in 2004.
UltraSPARC IV was created in 2005.