With Japanese forces establishing bases on Guadalcanal which threatened the sea route between the U.S. and Australia, Admiral King distributed the joint basic plan for the occupation and defense of Efate on 20 March 1942.

The US Navy's task was: (1) to construct, administer and operate a naval advance base, seaplane base, and harbor facilities; (2) to support Army forces in the defense of the island; (3) to construct an airfield and at least two outlying dispersal fields; (4) to provide facilities for the operation of seaplane-bombers.

[1] On 25 March 1942, the Army sent about 500 men to Efate from Noumea, and the 4th Defense Battalion, 45th Marines, arrived on 8 April.

[1]: 204 A detachment of Seebees went north to Havannah Harbour to construct a seaplane base to serve a squadron of PBYs.

By 1 June, the PBYs began operating from the new base, bombing the Japanese positions on Guadalcanal.