Key point: Japan lost the momentum at Coral Sea.
Many history books say the turning point of the Pacific War was the Battle of Midway in June 1942.
But a month before Midway, in a patch of ocean 3,500 miles away near the coast of Australia, there occurred another battle that could also be termed the turning point of the Pacific.
The Battle of the Coral Sea (May 4–8, 1942) has always been portrayed as the prologue to Midway—a sort of Midway-lite. Like Midway, it was a battle sparked by deciphered Japanese codes. And like Midway, it was an air-sea battle without any combat between surface ships; in fact, it was the first battle fought by fleets that never came within sight of each other.
But rather than a mere prequel to Midway, Coral Sea was a milestone: it put the first brakes on the Japanese Navy’s blitzkrieg across the Pacific.
For a time, Japan seemed unstoppable. In just five months, beginning with Pearl Harbor, the Rising Sun had shattered Allied power in the Pacific. Yet by May 1942, amid the euphoria of victory, Japanese leaders had to ask themselves a fundamental question: What next?
Japan now set its sights on Australia. Attempting to conquer the Land Down Under—even with the best Australian troops in North Africa fighting Rommel—would have strained Japanese military and logistical resources. However, by seizing airfields near Australia, they could isolate that Western outpost in the South Pacific from American supplies and reinforcements.
Japanese planners focused on capturing two locations. The first was the island of Tulagi, next to Guadalcanal Island, itself destined to become a battlefield three months later. But the more strategic objective was Port Moresby, on the southeastern coast of New Guinea and ideally placed for Japanese aircraft raiding Australia.
As so often in the Pacific War, it was Allied codebreakers who jammed the first stick into the imperial spoke. Deducing that Port Moresby would be the target of an amphibious assault, they alerted U.S. Pacific commander Adm. Chester Nimitz, who wanted to dispatch all four of America’s fleet carriers to the southwestern Pacific. But the Enterprise and Hornet had been sent on the Doolittle Raid, which left just the carriers Lexington and Yorktown. Considering that the Japanese could muster six aircraft carriers for the Pearl Harbor strike, Nimitz was taking a risk.