and RAAF units stationed in the town were sent to the Netherlands East Indies (Dutch East Indies; NEI) to strengthen the defences of the islands of Ambon and Timor. An improvised plan for support of the Philippines and the Dutch East Indies was completed in Washington on 20 December 1941 by the U.S. Army General Staff. It envisioned Darwin as the hub of transshipment efforts to supply those forces by landing supplies at Brisbane, shipping overland to Darwin, and onward by air and blockade-running ships. In reality, transport to Darwin by sea was necessary. Supplies and shipping intended both to build the Darwin base and to support the Java and Philippine forces were gathered in Darwin and the vicinity. In the two months before the air raids, all but 2,000 civilians were evacuated from the town. Japanese submarines I-121 and I-123 laid mines off Darwin in January 1942. By mid-February 1942 Darwin had become an important Allied base for the defence of the NEI. The Japanese had captured Ambon, Borneo, and Celebes between December 1941 and early-February 1942. Landings on Timor were scheduled for 20 February, and an invasion of Java was planned to take place shortly afterwards. In order to protect these landings from Allied interference, the Japanese military command decided to conduct a major air raid on Darwin. On 10 February a Japanese reconnaissance aircraft overflew the town, and identified an aircraft carrier (actually the seaplane tender ), five destroyers, and 21 merchant ships in Darwin Harbour, as well as 30 aircraft at the town's two airfields. Among the ships in harbour were those returned the morning before the attack from the convoy escorted by involved in the failed effort to reinforce Timor. Houston had departed for Java but left Mauna Loa and the Meigs which had attempted to transport Australian troops to Timor and the U.S. Army transports Portmar and Tulagi which had embarked a U.S. infantry regiment at Darwin. Prelude Opposing forces Despite Darwin's strategic importance to the defence of Australia, the city was poorly defended. The Australian Army's anti-aircraft defences comprised sixteen QF 3.7-inch AA guns and two 3-inch AA guns to counter aircraft flying at high altitude and a small number of Lewis Guns for use against low-flying raiders. The crews of these guns had conducted little recent training due to ammunition shortages. The air forces stationed in and near the town comprised No.