Johnson also had an abiding interest in politics, and served a term as the mayor of Highland Park, New Jersey from 1920 to 1922.

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.

[4] 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.,[3] 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.

During his tenure as chairman of the SWPC, Johnson personally oversaw war contracts assigned to more than 6,000 companies.

His tenure was a troubled one, and was marked by complaints from small businesses that they were not being awarded a significant portion of the most valuable wartime defense contracts.

[5] Johnson responded by increasing the number of contracts to small businesses; however, instead of examining each company to determine what contribution each could make to the war effort, the SWPC began distributing contracts as a form of relief to prevent setbacks to small concerns with unused factory plant capacity.

[5] As chairman of the SWPC and an Army general in the Ordnance Branch, Johnson had a tendency to overrule service branch requests for approval for production of specific military armament and ordnance items in favor of competing but less capable designs that could be made more rapidly or with lower material costs, freeing scarce but non-critical materials to small companies so that they could begin the transition to peacetime goods production.

[8] Unfazed, Johnson lost no opportunity in annoying his military superiors, frequently citing his business experience in support of his decisions.

Two days later, on October 1, 1943, Johnson resigned his chairmanship of the SWPC, citing ill health as the reason for his sudden departure.