The Allies chose the southern Solomon Islands including Guadalcanal, as the first target. The Imperial Japanese Navy (IJN) had occupied Tulagi in May 1942 and had constructed a seaplane base nearby. Allied concern grew when, in early July 1942, the IJN began constructing a large airfield at Lunga Point on Guadalcanal. From there, Japanese long range bombers would threaten the East Coast of Australia. By August 1942, the Japanese had about 900 naval troops on Tulagi and nearby islands and 2,800 people on Guadalcanal. These bases would protect Japan's major base at Rabaul, threaten Allied supply and communication lines and establish base for attacks against Fiji, New Caledonia and Samoa.