The Brewster F2A Buffalo was the first all-metal monoplane fighter to enter service with the US Navy in 1940, beating out the intial prototype Wildcat which had yet to achieve its future potential. Small and stubby-looking, the mid-wing Buffalo had a number of modern features such as a hydraulically-operated landing gear but was otherwise a rather lackluster aircraft due to its underpowered engine, weak armament, and lack of protection. The aircraft also suffered from considerable design and managerial delays, with Brewster taking two years to build the prototype. As a result, it lost favor with naval authorities once the revised Wildcat had been accepted into service. A handful of initial aircraft operated from the USS Saratoga and saw limited use with the USN, notably during the Battle of Midway flying with a land-based Marine squadron on the island which suffered heavy casualties. Nevertheless, the Buffalo was heavily exported mainly to Finland, Belgium, the Netherlands (many of the Belgian units ended up in British hands). All in all the F2A was not very successful except in the hands of the Finns during the Winter War with the Soviet Union in 1940 where it gave a good account of itself against poorly trained Soviet pilots flying even more obsolete aircraft; the Buffalo was credited with a kill ratio of 32:1 during the conflict. Most other Buffaloes were used by British Commonwealth and Dutch forces in the Far East where they were swept aside easily during the initial Japanese advance. They were quickly retired once superior aircraft became available.

The initial prototype XF2A-1 first flew in December 1937 and the initial F2A-1 became operational on board the USS Saratoga in late 1939. Follow up variants included the F2A-2 with an upgraded engine and the better-protected F2A-3 which also had a lenghtened fuselage as well as provision to carry bombs. The three variants could also be easily distinguished by having different propeller hubs: a skull cap spinner in the -1, a full spinner in the -2, and no spinner in the -3. Export versions were usually adapted from these variants, most of them modified for land-based use. These included the Model B-239 (F2A-1) for Finland, the B-339B (F2A-2) for Belgium, the B-339C and -339D (F2A-2) for the Dutch East Indies with different engines, the B-339E (F2A-2) for Britain (renamed Buffalo Mk. I and modified with numerous British equipment) and the B-439 (F2A-3) for the Dutch East Indies. Most of the latter were taken over by the USAAF and leased to the RAAF where they served serving in secondary duties.