We’ve talked about the hierarchy of the Army in the field, mostly discussing the tactical units at division and below. I’m re-reading Gen. Omar Bradley’s “A Soldier’s Story” about his campaigns in WWII, and I’ve just reached the point where he’s taken command of the First US Army. This seems an appropriate time to talk about the higher echelons of Army organization.
Whenever two or more divisions take the field, their operations are coordinated by a higher headquarters. Normally, this is a Corps (pronounced “Coors”) headquarters. In Vietnam, since the Vietnamese already had Corps headquarters for their army, the US Army named their equivalents “Field Forces” to avoid confusion. In Iraq, due to the semi-permanent nature of the headquarters, rather than having one of the numbered corps in place, they have created various “Multi-National Corps” headquarters. These are the functional equivalent of a regular tactical corps.
Where there are two or more corps deployed, the next echelon of command is a field army. In today’s Army, generally each theater of operations has its own numbered field army to command all Army units, often even when there is only one corps deployed. Field armies are permant standing organizations.
Should we find ourselves in such a large fight that two armies are deployed together, the next level of command would be an Army Group. For instance, in WWII, soon after the invasion of Normandy, the US First Army and the Third Army were in France. The 12th Army Group was activated to command them (with Bradley as the commanding general). Eventually the 9th Army would join the 12th Army Group. The campaign in Western Europe was so large that the Allies in Western Eurpope activated the 12th Army Group (US), 6th Army Group (US) and 21st Army Group (British). This didn’t count the 15th Army Group in Italy. Army Group headquarters are only formed when needed and are not a standing part of the Army’s peacetime organization.
No US war since WWII has been large enough to warrant the activation of an Army Group, but the ability to form a headquarters is still there. But the entire US Army isn’t large enough to warrant an Army Goup headquarters.