However, with the invasion of Bougainville, Rabaul was now directly jeapordized for the first time. Because the Battle of Empress August Bay had not turned out to Japan's advantage, she needed to act quickly to stomp out this threat. The Navy therefore reacted to reinforce Rabaul and prepare a counterstroke against the Bougainville invasion by moving a variety of additional cruisers to Rabaul. This was potentially very bad news for the Americans, because they had barely come away from the battle on the 2nd with a margin of victory. Against the forces now massing at Rabaul, there would be little chance of the American light surface units in the neighborhood of Bougainville prevailing. Furthermore, most of the US battleships and cruisers were elsewhere preparing for the invasion of Tarawa. In order to pre-empt a move by the Japanese, Rear-Admiral Frederick Sherman put together a bold operational plan to attack the Japanese force at its base. Racing in under a weather front with two carriers, Sherman relied on land-based airpower from New Guinea to protect his ships, while launching every one of his own planes to attack Rabaul. His sagacity was rewarded by near-total surprise and clear weather over the target.

Simpson's Harbor was crowded with ships, and most of them were refueling and in no way prepared to get underway. As they frantically cast off and scrambled for the harbor entrance, American aircraft had a field day. While no Japanese ships were sunk, many were damaged and would have to be sent back to Japan for months of repair work. Fewer than a dozen attacking aircraft were shot down. Upon recovering their aircraft, Sherman's raiders then raced away southward towards friendly aircover. The Japanese were unable to locate them before they escaped. Any Japanese hopes of contesting the Bougainville landings had vanished.

No one realized it at the time, but Rabaul was essentially finished as a prime naval base for the Japanese. Land-based airpower would now keep it under constant air attack, and its own airgroups would be steadily depleted. As time passed, Rabaul would become a backwater, it's garrison of nearly 100,000 men left to 'wither on the vine,' its large group of skilled aircraft mechanics left with less and less to do.

Carrier Raid on Rabaul	Japan	Allied
Starting Forces	x7 x3 x11	x1 x1 + escorts x97
Losses	x6 damaged (Atago, Maya, Chikuma, Mogami, Takao, Suzuya) x2 damaged (Agano, Noshiro) x3 damaged (Fujinami, Amagiri, Wakatsuki)	x10 destroyed