In March 1942 the City of Marysville and County of Yuba leased the airport and its 833 acres to the Army Air Forces to serve as air support command base for Marysville Cantonment (later named Camp Beale), and it was designated as Marysville Army Airfield. It was briefly used as a sub-base of Hamilton Field and controlled by the IV Fighter Command. One major unit served at Marysville Army Airfield, the 369th Fighter Group, a Replacement Training Unit that trained on A-36 Apaches, P-39 Airacobras, and P-40 Warhawks. The group had three fighter squadrons, the 398th, 399th, and 400th.