This was the US geographical rather than operational codename, changed to 'Button' in February 1943 and later still to 'Ebon', for Espíritu Santo island in the New Hebrides islands group (1941/45).
The New Hebrides islands group lies to the north-east of New Caledonia island and to the south-east of the Solomon islands group, and is a chain of about 83 mountainous and jungle-clad islands, 550 miles (885 km) long with a total land area of 4,706 sq miles (12189 km˛), aligned generally on a north-north-west/south-south-east axis. The chain splits in its northern half, and is therefore of a Y shape. The wet season is from November to April, when typhoons are possible, but the islands are wet and humid right round the year round, and malaria is a serious problem.
On the outbreak of the Pacific War, the islands were very sparsely populated, the largest settlement, Port Vila on Efate, having just 1,500 inhabitants in 1942, and the group’s overall population may have been in the order of only 40,000 persons in 1941. The islands were jointly controlled by the UK and France under a condominium agreed in 1906. The resulting duplication of effort did not help the quality of administration of an area lacking almost any economic significance before the war. Copra was the only valuable product, and the French imported 1,000 indentured labourers from French Indo-China. The British and Australians were forbidden by their governments to bring in labour, and their respective administrations came to outnumber those being administered.
As war loomed, the Australians began to raise a New Hebrides Defence Force in 1941: this eventually grew to a strength of more than 2,000 men, most of them from Malekula island.
During the 'Watchtower' campaign on Guadalcanal, the Allies established a major forward base at Espíritu Santo and a second base at Efate.
Espíritu Santo is the largest island of the New Hebrides group, extending 75 miles (120 km) along its north/south west coast and 45 miles (70 km) from east to west for a total land area of 1,527 sq miles (3955.5 km˛). In 1941 the island possessed a good but almost wholly undeveloped harbour at Luganville on the south-eastern part of the coast in a bay sheltered by Aore, Tutuba and Mallo islands. The western half of the island is mountainous with a maximum elevation of 6,165 ft (1879 m) at Mt Tabwemasana, and the eastern half is somewhat less rugged but with a number of limestone ridges, former reefs exposed by tectonic uplift. The climate is very damp, with an average annual rainfall of 90 in (230 cm), and the entire island was covered with jungle except where the land had been cleared for cultivation.
The native population was some 4,000 persons, and there were also about 900 Europeans. The island had produced copra, coffee, sugar cane, cotton, rice and tropical fruit at plantations were clustered largely in the south-east of the island and the adjacent smaller islands.
Given its strategic location, mid-way between New Caledonia and the Solomon islands group, Espíritu Santo became a major Allied base during the Guadalcanal campaign. An advance force from Efate arrived on 28 May 1942, and the US 3rd Naval Construction Battalion began to arrive on 12 August 1942. The initial airfield site, at Turtle Bay some 12 miles (19/25 km) to the north of Luganville, proved problematic, though Turtle Bay eventually boasted 6,000-ft (1830-m) and 4,500-ft (1370-m) runways, and by November 1942 there was a 6,000-ft (1,830-m) some 2 miles (3.2 km) to the west of Luganville and a 7,000-ft (2135-m) runway some 4 miles (6.4 km) to the east of Luganville. Early in 1943 a fifth runway, 6,800-ft (2070-m) long, was built outside Luganville.
The Allies initially tried to keep the existence of the base secret, but a reconnaissance floatplane from the submarine I-24 discovered the airfield on 2 October 1942.
Off Luganville, the Segond Channel is deep and well protected against the elements, and this was developed during the war into the largest operating base in the South Pacific with an importance with survived to the end of the war. The base was dismantled on 12 June 1946.