In 1939, the U.S. Army issued Circular Proposal 39-775 for new fighters that could utilize new engines. Of the four companies that submitted designs, Grumman submitted Design 41 which was largely based on Design 34 (XF5F-1) but would utilize two Wright R-1820 radial engines. Although Lockheed’s design was deemed more favorable, the Army wanted Grumman to continue revising Design 41 as a backup in case Lockheed’s proposal ran into hiccups.