text: Armies
  Land Component Commands in World War II
  Having a land component commander is not new to the Armed Forces of the United
  States. The Allies in World War II successfully employed separate joint or multinational
  land component commander headquarters in several theaters. These land component
  commands ensured proper coordination with other components and freed the
  multinational force commander to focus on overall strategy. After the Allied losses at
  the battle of the Kasserine Pass in February 1943 due to poor command relationships,
  General Dwight D. Eisenhower restructured his Allied Forces in North Africa. Not only
  were all air elements brought under centralized control, but all land forces were also
  consolidated under General Sir Harold Alexander’s 18th Army Group. This structure
  was the first modern combined organization with coequal land, maritime, and air
  component commanders under separate commanders, and it contributed significantly
  to the defeat of the Axis in North Africa by May 1943. For the Normandy invasion in
  June 1944, Eisenhower again subordinated U.S. Army forces under a multinational
  land component commander, British Field Marshal Bernard Law Montgomery.
  LIMITATIONS
  3-145. The limitations of the field army include—
  * The field army does not have permanently assigned forces.
  * The field army does not have aligned Air Force theater air control system liaison elements (if the
  field army is not the land component).
  * There are no standing field armies in theaters with peer adversaries who will challenge the joint
  force’s ability to respond.
  * The Army constitutes a field army when a JFC or theater army commander perceives a
  requirement to command and control multi-corps operations, until then the GCC incurs risk.
  * The time required to constitute a field army depends upon how quickly additional capabilities can
  be brought into theater. In OEs where an enemy has significant preclusion capabilities, this could
  be so long that it may not be possible to deny enemy operational and strategic objectives at
  acceptable cost.