The nearly 2,000 to 3,000 Japanese personnel on the islands were taken by surprise, and by nightfall on August 8, the 11,000 Allied troops, under the command of Lieutenant General Alexander Vandegrift, secured Tulagi and nearby small islands as well as the Japanese airfield under construction at Lunga Point on Guadalcanal, later renamed "Henderson Field" by the Allies. Allied aircraft operating from Henderson were called the "Cactus Air Force" (CAF) after the Allied code name for Guadalcanal. To protect the airfield, the US Marines established a perimeter defense around Lunga Point. Reinforcements over the next two months increased the number of US troops at Lunga Point on Guadalcanal to more than 20,000.