Several nations, including Finland, Belgium, Britain and the Netherlands, ordered the Buffalo. Of all the users, the Finns were the most successful with their Buffalos, flying them in combat against early Soviet fighters with excellent results. During the Continuation War of 1941–1944, the B-239s (a de-navalized F2A-1) operated by the Finnish Air Force proved capable of engaging and destroying most types of Soviet fighter aircraft operating against Finland at that time and achieving in the first phase of that conflict 32 Soviet aircraft shot down for every B-239 lost, and producing 36 Buffalo "aces".
In December 1941, Buffalos operated by both British Commonwealth (B-339E) and Dutch (B-339D) air forces in South East Asia suffered severe losses in combat against the Japanese Navy's Mitsubishi A6M Zero and the Japanese Army's Nakajima Ki-43 "Oscar". The British attempted to lighten their Buffalos by removing ammunition and fuel and installing lighter guns to increase performance, but it made little difference. After the first few engagements, the Dutch halved the fuel and ammunition load in the wing, which allowed their Buffalos (and their Hurricanes) to stay with the Oscars in turns.
The Buffalo was built in three variants for the U.S. Navy, the F2A-1, F2A-2 and F2A-3. (In foreign service, with lower horsepower engines, these types were designated B-239, B-339, and B-339-23 respectively.) The F2A-3 variant saw action with United States Marine Corps (USMC) squadrons at the Battle of Midway. Shown by the experience of Midway to be no match for the Zero, the F2A-3 was derided by USMC pilots as a "flying coffin." The F2A-3s performance was substantially inferior to the F2A-2 variant used by the Navy before the outbreak of the war despite detail improvements.
Even in late 1940 it was apparent that the Buffalo was rapidly becoming obsolete. It badly needed a more powerful engine, but the limits of the airframe had been reached, making installation of a larger engine impossible. Soon after deliveries of the F2A-3 began, the Navy decided to eliminate the type altogether. By then, considered a second line aircraft, some were transferred to the U.S. Marine Corps, which deployed two F2A-3 squadrons to the Pacific, one at Palmyra Atoll, and another at Midway Island. Those which still remained on board aircraft carriers narrowly missed a combat opportunity when a relief mission was dispatched to Wake Island, but the relief force was withdrawn before completing the mission. Shortly thereafter, F2A-3s still in naval service were transferred to training squadrons for use as advanced trainers.