In May 1942, things were going Japan’s way. Since their surprise attack on U.S. forces at Pearl Harbor the previous December, the Japanese had struck Allied targets across the Pacific and Far East, seizing Burma (Myanmar), the Dutch East Indies (Indonesia) and the Philippines, as well as Guam and Wake Island.

As a knockout blow, the Imperial Japanese Navy, led by Admiral Isoroku Yamamoto, plotted a large-scale attack on the strategically important U.S. naval and air base on Midway Atoll, two tiny islands in the central Pacific. If successful, Yamamoto believed, the Midway attack would crush the U.S. fleet, winning the Pacific War for Japan.

Things didn’t turn out that way.

Instead, it was the Japanese who were caught off guard on June 4, 1942, and the Americans who would go on to score a momentous victory in the Pacific theater. Here are five little-known facts about the Battle of Midway, and its impact on World War II in the Pacific.

In addition to naval codebreaking that gave Admiral Chester Nimitz advance warning of Japan’s plan of attack, the U.S. fleet benefited from another key technological advance at Midway: radar. The U.S. Naval Research Laboratory (NRL) had developed the first radar system prototype by 1938, and early radar systems were placed aboard carriers and other ships leading up to the Pearl Harbor attack.

At Midway, all three U.S. carriers and some supporting vessels benefited from radar, which allowed them to detect approaching Japanese aircraft at long range and better prepare for their attacks. In contrast, the Japanese ships relied solely on human lookouts, allowing U.S. dive-bombers to remain undetected until virtually the moment they reached attack position.

By chance, none of the three U.S. aircraft carriers in the fleet at the time were at Pearl Harbor on December 7, 1941; all were out to sea on maneuvers, and all escaped unscathed.

This failure would come back to haunt the Japanese in May 1942, when the first major carrier battle took place in the South Pacific. The Battle of the Coral Sea, in which Allied forces turned back Japan’s invasion of Port Moresby in New Guinea, was the first naval battle in history in which the ships involved never sighted or fired directly at each other.

The Battle of Midway confirmed the carrier’s emergence as the key naval vessel in World War II, displacing the battleship. Nimitz rushed three U.S carriers—the Enterprise and Hornet, which had participated in Col. James Doolittle’s raid on Tokyo in April 1942, and the Yorktown, which was damaged in the Coral Sea—to the central Pacific, laying a trap for the Japanese.

Meanwhile, Yamamoto’s two most modern carriers, the Shokaku and Zuikaku, had been damaged in the earlier battle, and were unavailable for use at Midway.

On May 27, 1942, the USS Yorktown struggled into Pearl Harbor, after traveling 3,000 miles across the Pacific. During the Battle of the Coral Sea, a 551-pound Japanese bomb had hit the Yorktown’s wooden flight deck, smashing through and exploding inside the ship. More than 1,400 repairmen worked around the clock, patching the holes in the Yorktown with steel plates, in order to have it ready for Nimitz at Midway.

After barely 48 hours in Drydock Number One at the Pearl Harbor Navy Yard, the Yorktown steamed out to join the Hornet and Enterprise 325 miles north of Midway, at a predetermined meeting spot known as “Point Luck.” The Yorktown’s presence caught Japan by surprise; they had thought they had disposed of the carrier in the Coral Sea.

Japanese counterattacks from bombers and submarines sank the Yorktown on June 7, 1942, but not before it managed to play a key role in the Allied victory at Midway.

In 1998, the Yorktown was finally located some 16,650 feet under the surface of the Pacific, by a team led by Robert Ballard, the undersea explorer known for discovering another famous wreck: the Titanic.