In preparation for the offensive, in May, U.S. Major General Alexander Vandegrift was ordered to move his 1st Marine Division from the U.S. to New Zealand. Other Allied land, naval, and air force units were sent to establish bases in Fiji, Samoa, and New Caledonia. Espiritu Santo in the New Hebrides was selected as the headquarters and main base for the impending offensive—codenamed Operation Watchtower—with the commencement date set for 7 August. At first, the Allied offensive was planned just for Tulagi and the Santa Cruz Islands, omitting Guadalcanal. However, after Allied reconnaissance discovered the Japanese airfield construction efforts on Guadalcanal, capturing that airfield was added to the plan and the Santa Cruz operation was dropped.