 The 4th Army was assigned and supported by the 5th Army, which would come to its aid when needed.The Fengtian Air Force was headquartered at Shenyang, with three groups mobilized for the war effort.Two of these groups were under the direct command of the Combined Corps of Fengtian army, while the remaining one was deployed to Yi County, under the direct command of Zhang Xueliang's 2nd Army.