In 1942, Johnson's reserve Army commission was activated, and he was promoted to the rank of brigadier general and assigned to the Ordnance Department. That same year he was nominated by the Roosevelt administration to be vice-chairman of the board of the War Plants Corporation (WPC). When the Smaller War Plants Corporation (SWPC) was established as a division of the WPC in June 1942, Johnson was named chairman of the board of the SWPC., which regulated wartime production of military goods and defense items in smaller defense plants and businesses (500 or fewer employees) dispersed throughout the U.S. economy. The SWPC made direct loans, encouraged commercial lenders to make credit available to small businesses, and advocated for small businesses with federal agencies and larger corporate enterprises.