What was significant about the United States victory at the battle of Midway

Japanese had planned to capture a strategic island in the middle of the Pacific Ocean, home to an Am. military base. The Jap's wanted to lure the Am's into a battle they were sure to lose. Am's had broken the Jap. code though, so they could understand the messages. Am. admiral Chester Nimitz planned an effective defense and it worked perfectly, with the Am's destroying 4 Jap. aircraft carriers and winning a great victory.