Ordered to the field on 8 May 1942, Benner joined Company "A", 1st Battalion, 7th Marines, and, after traveling by rail to Marine Corps Recruit Depot San Diego, sailed for the South Pacific in late May. After arriving at Tutuila, the battalion reinforced other elements of the 7th Marines already on garrison duty in the Samoan Islands. It remained there, serving as a reserve amphibious force, during the initial landings on Guadalcanal in early August. While on Samoa, Sgt. Benner accepted appointment as second lieutenant on 4 August. The 7th Marines sailed from Samoa on 4 September, for Espiritu Santo in the New Hebrides. Upon arrival on the 12th, the regiment received orders to move to Guadalcanal as soon as possible. Departing the New Hebrides on the 14th, the transports arrived off Kukum, Guadalcanal, on 18 September. Later that same day, the 7th Marines took up a position astride "Bloody Ridge", guarding the perimeter's southern flank from there down to the Lunga River.