Lt. Edward “Butch” O’Hare, Feb. 1942

On Feb. 20, 1942, the flattop Lexington was steaming toward the Japanese base at Rabaul, Papua New Guinea, when it was approached by two enemy flying boats. Their crews managed to signal its coordinates before American fighters flamed the planes, and the Japanese immediately launched an attack against Lexington.

That chance encounter had dire implications for the U.S., which couldn’t afford the loss of a single ship and certainly not a carrier.

American radar picked up two waves of Japanese aircraft. Mitsubishi G4M1 “Betty” bombers—good planes with experienced pilots.

Six American fighters led by legendary pilot Jimmy Thach intercepted one formation, breaking it up and downing most of the Bettys.

The second wave, however, approached from another direction almost unopposed.

Almost.

Two American fighters were close enough to intercept the second flight of eight bombers. The Navy pilots flew Grumman F4F-3 Wildcats, which like…