IV Army Corps - Greece - was created in 1914.
IV Corps - Pakistan - was created in 1965.
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.
IV SS Panzer Corps was created in 1943.
IV Corps - United States - was created in 1939.
IV Corps - United Kingdom - was created in 1940.
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.
No, there is not.
From the Mekong Delta (IV Corps) to the DMZ (I Corps); from the China Sea to the borders of Laos & Cambodia. RVN was blanketed with GIs.
Anywhere they were at was VC territory. But primarily in the Mekong Delta; the NVA had a long enough distance to march as it was (down the Ho Chi Minh Trail from North Vietnam), so the NVA operated in III Corps (Saigon AO) only during the Tet Offensive and related actions, then stayed in the Highlands (II Corps) and I Corps regions; leaving the Delta (IV Corps) to the VC. In the 1970's, (generally speaking) III & IV Corps (MR=Military Regions 3 & 4) were VC country and II and I Corps were NVA territory. With I Corps being the worst (place to be). In I Corps, the NVA hunted for you (the GI).