World War II, the 1st MarDiv began intensive training and preparation for combat deployment. Gayle was promoted to the rank of captain in May 1942 and left with the division by navy transport the Pacific, en route evading German torpedo attack and then transitting the Panama Canal and continuing to New Zealand, while other elements of the 1st MarDiv left the United States for New Zealand by sea from San Francisco. One month later, in Wellington, the division reloaded its ships for amphibious assault and was then ordered under its commanding officer Major General Alexander A. Vandegrift to Guadalcanal, Solomon Islands, in early August 1942. Gayle was appointed operations officer of 1st Battalion, 5th Marines and took part in the initial landing on Guadalcanal on August 7 and capture of the Japanese airfield under construction. The construction was finished by Seabees and Marine engineers and named Henderson Field one day later. Some days later, and after U.S. Navy units had been compelled to withdraw temporarily from the Guadalcanal area, Gayle while on battalion-level reconnaissance outside the Henderson Field perimeter, discovered a powerful working radio that the retreating Japanese had left behind. Gayle received orders to destroy the radio because of the possibility that it was booby-trapped and because of general revulsion, after the notorious Goettge Patrol incident, among many officers for the taking of Japanese souvenirs. Finding no evidence of sabotage and recognizing the potential utility of a powerful radio, Gayle left the radio intact. Following heavy ship losses during the Battle of Savo Island, Vice Admiral Richmond K. Turner temporarily withdrew naval forces from the immediate Guadalcanal area, including the transports holding key undelivered Marine supplies and equipment. Until naval units, under the inspirational leadership of Admiral William "Bull" Halsey returned to continue their ultimately successful but heavily contested and heroic support for the 1st Marine Division on Guadalcanal, the only means of long-range communication available to the hard-pressed Division was the Japanese radio Gayle had identified and safeguarded. Gayle participated in the grueling fighting for control of Guadalcanal which continued throughout the fall and winter of defense of Henderson Field 1942. Along with the rest of the 1st Marine Division Gayle left Guadalcanal when they were relieved by U.S. Army units in December 1942. The division sailed to Australia for rest and refit, in Brisbane and later in Melbourne. Gayle was stationed at Camp Balcombe near the town