The Battle of Midway, which was a victory for the U.S. Navy, was important because it was effectively the turning point of World War II in the Pacific. Prior to the Battle of Midway, the Japanese had not lost a sea battle fought on the Pacific or Indian Ocean; they held a significant military advantage, in part because they possessed the strongest air carrier unit in the Pacific.
The Battle of Midway occurred after Japanese Admiral and fleet commander Isoruku Yamamoto started an aggressive operation to occupy the two islands of the Midway atoll. The Japanese planned to use the carriers in their navy, led by Vice-Admiral Nagumo, to ambush U.S. Navy ships and carriers that had sortied from Pearl Harbor in response to the Midway operation.
Rather than being ambushed, the U.S. Navy instead managed to ambush the Japanese Navy, resulting in the sinking of four Japanese carriers in a single day of battle on June 4, 1942. The U.S. Navy only suffered the loss of a single carrier.
The U.S. victory at Midway gave the U.S. Navy in the Pacific the military advantage over the region. The battle also halted the Japanese Navy's progress across the Pacific and placed them in a reactionary position for the rest of World War II.