The battle of Midway was an early turning point in WWII between Japan and the US. It was fought in the middle of the Pacific Ocean, the Japanese v. the Americans June 1942.
6 months earlier in Dec. 1941 the Japanese had started the War against the US by clobbering it's fleet at Pearl Harbor, about half the US Pacific fleet was knocked out. The Japanese next plan was to finish off the US in the Pacific by attacking Midway island.
US Midway Island sat in about the middle of the Ocean, but was close to US Hawaii. If the Japanese had Midway the US Hawaiian islands would not be safe and the US would have to retreat out of the ocean all the way back to California.
The Japanese plan was to send it's fleet, at that time 4 times the size of the damaged American fleet to Midway island. Half of the Japanese armada would take the island over, while the other half held back. The Americans couldn't afford to let the Japanese stay there and lose the War in the Pacific so they would have to send what was left of their fleet to hit the Japanese force holding the island. When they did the other Japanese force would jump out and the US force would be destroyed from 2 sides by a Japanese force 4 times bigger....That was the plan.
However....The Americans had broken the Japanese military code, and knew the Japanese plan ahead of time. They sent their fleet to Midway first, before the Japanese got there and had it wait out in the ocean where the Japanese wouldn't see it. When the Japanese showed up attacked the island and started setting up their plan, the American fleet jumped out and ambushed them.
Although only 1/4 as big the US fleet destroyed 4 Japanese aircraft carriers, a bunch of their planes and other ships in 1 of the biggest naval upsets ever. The result of the big US victory was the Japanese had to retreat, back to their side of the Ocean, while the Americans held the center. It saved Hawaii in the center of the ocean as the US headquarters from where they could conduct the Pacific war against Japan, totally defeating Japan by August 1945.