Initially deployed as part of the headquarters of Marine Aircraft Group 23, this detachment established an SCR-270 long range radar that allowed the Cactus Air Force to husband its critically short fighter assets during the early stages of the battle when control of the island was still very much in doubt.

Combat lessons learned from this detachment had a great deal of influence on the Marine Corps' development of its own organic, large scale air warning program which began in early 1943.

[2][3] Dermott H. MacDonnell enlisted into the Marine Corps in Boston, Massachusetts on 9 April 1942, and immediately attained the rank of Staff Sergeant based on previous technical experience.

[11] On 7 August 1942, the First Marine Division landed on Tulagi and Guadalcanal at Lunga Point, capturing the partially completed Japanese airfield and marking the first counter-offensive taken by the Allies in the Pacific Theater.

[14] When the Navy's carriers departed early in the campaign, it became readily apparent that the Marine Corps had failed to properly plan for land based fighter direction.

[19][20] Air battles between Allied aircraft at Henderson and Japanese bombers and fighters from Rabaul continued almost daily for the opening months of the campaign.

The eight-hour round-trip flight from Rabaul to Guadalcanal, about 1,120 miles (1,800 km), seriously hampered Japanese efforts to establish air superiority over Henderson Field.

The detachment's gear was unable to get ashore that day as the ships quickly steamed off for the safety of Tulagi harbor based on reports of an incoming Japanese air raid.

The individual radars provided information via landline to the firing batteries of the 3d Defense Battalion and to the 1st Marine Aircraft Wing's fighter directors led by LtCol Bayler.

[27][15] Upon receiving radar reports of an incoming Japanese air raid, the fighter director was driven, in a special communications truck outfitted with a salvaged radio from a wrecked Grumman F4F Wildcat, to a control center about a mile away that had been dug into the side of a hill.

[30] During the course of the battle the men and equipment of the radar detachment were constantly exposed to enemy small arms fire, artillery shelling, naval gunfire, and aerial bombardment.

[27] In 1 November MAW Control Center migrated to a dugout in the side of a hill that offered better protection against enemy fires, improved air-ground communications, and enhanced coordination between fighter directors and ground based air defense units.

The Marine Corps attached three officers and a senior NCO to this detachment, led by Major Ethridge C. Best, to assist with training and to provide liaison with American fighter units.

Instead of maintaining a permanent combat air patrol overhead, fighters were held on the ground until Japanese aircraft were inbound from the Northern Solomon Islands.

[38] This detachment was never part of the early lore of the Cactus Air Force immediately after the battle because radar was still a top secret technology thus its contributions were never properly added as the first stories from Guadalcanal were being written.

[42] VMF(N)-531, with its GCI Detachment, deployed overseas in August 1943 and eventually controlled the first successful night interception in the Pacific working with an F4U-2 Corsair from the U.S. Navy's VF(N)-75.