Brown approached Rabaul after the intended ANZAC reinforcement fell away because its fuel supply could not support the operation. Japanese reconnaissance then removed surprise while land-based aircraft grew more numerous as Task Force 11 closed the heavily defended hub. Pressing on would have exposed Lexington and her reduced surface screen to concentration and possible ambush. Brown abandoned the strike once surprise and the intended reinforcement were lost. Even the attempted approach made Japan strengthen Rabaul, demonstrating that a credible carrier threat could divert forces without reaching its target.
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Why Task Force 11 broke off the Rabaul raid
Japanese reconnaissance removed surprise, inadequate fuel kept the intended ANZAC reinforcement away, and Rabaul's concentrated air strength made continuing the approach too dangerous.