US Navy orders followed as did some (with Wright Cyclone engines) from France; these ended up with the Royal Navy's Fleet Air Arm after the fall of France and entered service on 8 September 1940. These aircraft, designated by Grumman as G-36A, had a different cowling from other earlier F4Fs and fixed wings, and were intended to be fitted with French armament and avionics following delivery. In British service initially, the aircraft were known as the Martlet I, but not all Martlets would be to exactly the same specifications as US Navy aircraft. All Martlet Is featured the four .50 in (12.7 mm) M2 Browning machine guns of the F4F-3 with 450 rpg. The British directly ordered and received a version with the original Twin Wasp, but again with a modified cowling, under the manufacturer designation G-36B. These aircraft were given the designation Martlet II by the British. The first 10 G-36Bs were fitted with non-folding wings and were given the designation Martlet III. These were followed by 30 folding wing aircraft (F4F-3As) which were originally destined for the Hellenic Air Force, which were also designated Martlet IIIs. On paper, the designation changed to Marlet III(A) when the second series of Martlet III was introduced.
Poor design of the armament installation on early F4Fs caused these otherwise reliable machine guns to frequently jam, a problem common to wing-mounted weapons of many US fighters early in the war. It was an F4F-3 flown by Lieutenant Edward O'Hare that in a few minutes shot down five Mitsubishi twin-engine bombers attacking Lexington off Bougainville on 20 February 1942. But contrasting with O'Hare's performance, his wingman was unable to participate because his guns would not function.
A shortage of two-stage superchargers lead to the development of the F4F-3A, which was basically the F4F-3 but with a 1,200 hp (890 kW) Pratt & Whitney R-1830-90 radial engine with a more primitive single-stage two-speed supercharger. The F4F-3A, which was capable of 312 mph (502 km/h) at 16,000 ft (4,900 m), was used side by side with the F4F-3, but its poorer performance made it unpopular with US Navy fighter pilots. The F4F-3A would enter service as the Martlet III(B).
At the time of Pearl Harbor, only Enterprise had a fully equipped Wildcat squadron, VF-6 with F4F-3As. Enterprise was then transferring a detachment of VMF-211, also equipped with F4F-3s, to Wake. Saratoga was in San Diego, working up for operations of the F4F-3s of VF-3. 11 F4F-3s of VMF-211 were at the Ewa Marine Air Corps Station on Oahu; nine of these were damaged or destroyed during the Japanese attack. The detachment of VMF-211 on Wake lost seven Wildcats to Japanese attacks on 8 December, but the remaining five put up a fierce defense, making the first bomber kill on 9 December. The destroyer Kisaragi was sunk by the Wildcats, and the Japanese invasion force retreated.
In May 1942, the F4F-3s of VF-2 and VF-42, onboard Yorktown and Lexington, participated in the Battle of the Coral Sea. Lexington and Yorktown fought against the Zuikaku, Shōkaku and the light carrier Shōhō in this battle, in an attempt to halt a Japanese invasion of Port Moresby on Papua. During these battles, it became clear that attacks without fighter escort amounted to suicide, but that the fighter component on the carriers was completely insufficient to provide both fighter cover for the carrier and an escort for an attack force. Most US carriers carried less than 20 fighters.