Concerned that he had lost the element of surprise, Omori radioed Samejima to ask permission to send the slow-moving transports back to Rabaul, but to continue with the combat ships to attack the American transports that he assumed were still in Empress Augusta Bay. Samejima concurred, and Omori pressed ahead with his cruisers and destroyers. At the same time, Rear Admiral Stanton Merrill was steaming toward the Bay with four light cruisers and eight destroyers. The two forces met in the early morning hours of 2 November in the Battle of Empress Augusta Bay, in which the Japanese lost the light cruiser Sendai and the destroyer Hatsukaze. Carrier raid on Rabaul Admiral Koga was unwilling to risk his precious aircraft carriers, but decided to dispatch seven heavy cruisers to Rabaul. These arrived on 3 November. News of the cruisers' arrival in the area of operations greatly concerned Admiral Halsey: the Bougainville beachhead was still quite vulnerable and he had no heavy cruisers at all to oppose a bombardment. Taking a huge gamble, he ordered the only carrier force under his immediate command, Task Force 38 under Rear Admiral Frederick C. Sherman, to cripple or sink as much of the combat shipping in Simpson Harbor as possible. The resulting air strike, launched from Sherman's fleet carrier Saratoga and light carrier Princeton on 5 November, with fighter escorts being provided by land-based aircraft from Air Solomons command and followed up by land-based aircraft from the Fifth Air Force, sank no ships but inflicted enough damage to convince Koga to withdraw the heavy cruisers, without having been able to attack the beachhead. A second raid was launched on 11 November with aircraft from the Essex, Bunker Hill and Independence, along with a sizeable force of land-based B-24 bombers. The use of land-based heavy bombers against the Japanese ships proved ineffective, but the carrier-based aircraft achieved a degree of success, sinking a destroyer and damaging three destroyers and two cruisers. November 1943: expanding the beachhead Early November Defense and expansion of the US lodgment at Cape Torokina involved protracted and often bitter jungle warfare, with many casualties resulting from malaria and other tropical diseases. Except for patrol skirmishes, all of the major combat to expand the beachhead occurred in the Marine sector. From 6 to 19 November, the remaining regiment of the 3rd Marine Division and the US Army 37th Infantry Division were landed