Authorities were as astonished as the Japanese attackers had been by the savage and effective response of the two PTs to the massive attack which should have wiped them out, according to all the rules. Smaller and less determined air attacks had sunk cruisers and destroyers in other waters. Commander Mumma, with justifiable pride in his two boats, said of the action: “It has shown that the automatic weapon armament is most effective. It has demonstrated that ably handled PTs can, in daylight, withstand heavy air attack.” On the same Christmas Day 1943, the Bougainville bomber strip went into business, and the fighter strips were so well established that American forces could afford to settle down behind the barbed wire of The Perimeter, content with what they already held. From here on out, they could afford to ignore as much as possible the 15,000 Japanese still on the island. From that day Rabaul was doomed to comparative impotence under a merciless shower of bombs. Not that Rabaul was a feeble outpost. One hundred thousand Japanese soldiers, behind powerful fortifications and with immense supplies, made Rabaul a formidable fortress—too tough for a direct frontal assault—until the end of the war. Without air power, however, the Japanese there could do nothing to hold back the Allied advance except to glower at the task forces passing by just out of gun range on their way to new island bases farther up the line. The Japanese gate was unhinged at both ends and the Allies poured through the gap. American strategists decided to jump over Rabaul, leaving its defenders to shrivel away behind a sea blockade. Some of the PTs leapfrogged with the rest of the Allied forces and readied for more night patrol in the waters farther along the sea lanes to Tokyo; some of them stayed behind to make life as miserable as possible for the bypassed Japanese on Bougainville and the other islands cut off from home. PTs played a big part in the last jump that isolated Rabaul. The landings in the Admiralty Islands were on Leap Year Day, February 29, 1944, by units of the First Cavalry Division. The Admiralty Islands are a ring of long, thin islands enclosing a magnificent anchorage called Seeadler Harbor. The fine anchorage and the airstrips planned for the islands would give the Allies the last brick in the wall around Rabaul. Faulty reconnaissance from the air had shown that the islands were free of Japanese. Actually there were 4,000 Japanese in the islands, and their commander was insulted that the Americans landed a force only a fraction the size of his. He counterattacked violently. The only Navy fire support available was from destroyers and small craft. Among the small craft were MTB Squadron Twenty-One, commanded by Lieutenant Paul Rennell, and Squadron Eighteen, commanded by the same Lieut. Commander H. M. S. Swift who had surprised the Japanese air command by the vicious antiaircraft fire of his two torpedo boats near Arawe on Christmas Day.