In 1942 the United States Navy built a major forward base on Funafuti to support the central Pacific campaign against Japan. At its peak the atoll hosted tens of thousands of personnel, a long-range airstrip (later the international airport), a seaplane base, fuel storage, and a network of gun emplacements scattered across the islets. From here, B-24 bombers flew sorties against the Gilbert and Marshall Islands.
What remains today is scattered and unmarked but unmistakable once you start looking: bunker walls in the bush on Tepuka and other islets, the foundations of fuel tanks behind Vaiaku, lengths of corroded pipework, anti-aircraft gun positions on the ocean side, and the wreckage of aircraft visible in the lagoon at low water. Locals will point things out if you ask. No formal tour exists — wander, ask, and you will find more than you expect.