assisted the navy in defending Simpson Harbor. An effective early warning radar system provided coverage from Rabaul, and extended coverage with additional radars on New Britain, New Ireland, and at Buka. These sets provided from 30 to 60 minutes' early warning of an attack. Land-based air campaign As a part of Operation Cartwheel, in the fall of 1943 the U.S. Fifth Air Force, the Royal Australian Air Force and the Royal New Zealand Air Force, all under the command of General George Kenney, began a sustained bombing campaign against the airfields and port of Rabaul. The initial mission was delivered by 349 aircraft on 12 October 1943, but it could not be followed up immediately due to bad weather. A single raid by 50 B-25 Mitchell medium bombers reached the target on 18 October. Sustained attacks resumed on 23 October, culminating in a large raid on 2 November. In the 2 November mission, nine squadrons of B-25s, 72 bombers in total, and six squadrons of P-38 Lightning totaling 80 fighter escorts attacked Simpson Harbor and its anti-aircraft defenses with bombing attacks and minimum altitude strafing runs. Eight B-25s were shot down by AAA or Japanese naval fighters. Nine of the P-38s were also lost. Among the lost was Major Raymond H. Wilkins of the 3rd Attack Group, who was posthumously awarded the Medal of Honor. Carrier attacks The Navy had not contemplated an air attack upon Rabaul. Admiral William Halsey was implementing the next phase of his advance up the Solomon chain, and looked to establish a base on Bougainville. On Bougainville the Japanese had two airfields at the southern tip of the island, one at the northernmost peninsula, and a fourth on Buka just across the northern passage. Instead of attempting a costly assault on these heavily defended areas Halsey landed his invasion force of 14,000 Marines at Empress Augusta Bay, about halfway up the west coast of Bougainville. There he would have his Seabees clear and build an airfield of their own. On the first night the screening naval unit succeeded in defending the landing (the Battle of Empress Augusta Bay), but Admiral Mineichi Koga responded quickly. Within a few days the local cruiser force had been augmented with reinforcements from Truk. The Japanese had been conserving their naval forces over the past year, but in the face of the imminent threat to Rabaul now committed substantial resources