in order to concentrate on his primary role, he largely delegated responsibility for running GHQ to McNair. As part of this working relationship, Marshall provided McNair broad advice and guidance, and McNair obtained approval from Marshall for the most important decisions. As GHQ's responsibilities increased following U.S. entry into the war, McNair's responsibilities were encroached upon by members of the War Department staff; for instance, the logistics staff section (G-4) retained authority over corps area commands in matters involving billeting, equipping, and supplying soldiers undergoing mobilization training, which limited GHQ's ability to plan them and oversee their execution. In response, McNair proposed establishing GHQ's unity of command over the Army's four field armies and eight corps areas; under his concept, each corps area headquarters would have responsibility for all administrative functions within their areas of responsibility, enabling GHQ and the field armies, corps, and divisions to focus on organizing, training, and administering the mobilized troop units that were preparing to go overseas. Though Marshall was initially receptive, members of the War Department General Staff disagreed with McNair's proposal, and Marshall concurred with them. The small GHQ staff Marshall assembled included representatives from each of the Army's major field branches – Infantry, Field Artillery, Cavalry, Coast Artillery, Armor, Engineers, and Signal, along with liaison officers representing the National Guard and Army Reserve. As operations tempo increased, the staff expanded to include functional area representatives (G-1, G-2, G-3, and G-4). Among the individuals who served on the GHQ staff were Lloyd D. Brown, who later succeeded Omar Bradley as commander of the 28th Infantry Division, and Mark W. Clark, who went on to command the 15th Army Group. McNair's National Guard liaison was Kenneth Buchanan, who later served as assistant division commander of both the 28th and 9th Infantry Divisions, and commanded the Illinois National Guard as a major general after the war. As GHQ chief of staff, McNair played a leading role in planning and conducting the 1940 and 1941 Louisiana Maneuvers and Carolina Maneuvers, large scale war games that enabled the Army to observe and draw conclusions with respect to training, doctrine, leadership, and other items of interest, which in turn led to changes in doctrine, equipment, and weapons. In addition, these maneuvers were used to identify which senior officers were most capable, enabling the Army to assign the best performers to command and top level staff positions, and relieve