The first major Navy Fleet Action of the Pacific Theater in World War II was the battle fought May 7th and May 8th between Imperial Japanese Navy Forces and Allied forces, including the United States Navy and Australia. In addition it was the first Navy battle that featured aircraft carriers in battle at a distance from each other. Neither ship was in line of sight to the other, and the battle was mainly fought by the aircraft carrier based military Navy planes that took the battle to the others ship.
Neither of the ships fired upon the other, and the U.S. Navy and U.S. Navy aircraft bravely fought the battle. While it was considered a tactical victory for the Japanese Forces, there was the loss of the light carrier Shoho from the Japanese Imperial Navy. The US Navy lost the carrier USS Lexington, although most of its crew were rescued.
The battle served several purposes, some of which were not readily apparent. There was no clear victor at first, but there was valuable experience gained by commanders and US Navy leaders, which set up the Allied Naval Victory at Midway Island 29 days later. Also, because of the Battle of the Coral Sea, the Japanese Imperial Forces gave up on their plans to advance on New Guinea. The Japanese had systematically advanced up to that point, and their plans included a ground invasion of Port Moresby, New Guinea, to be used as a Pacific theater command center, but because the plan was abandoned never came to pass.
The Japanese began the conflict with the attack five months previous to the Coral Sea conflict by their sneak attack on Pearl Harbor Hawaii on December 7th, 1941. Japan was flush with pride and they believed that nothing would slow their advance across the Pacific. The Allied forces before the Battle of the Coral Sea had suffered a series of discouraging and humiliating defeats, and the Battle of the Coral Sea was largely a draw, but suffered as a valuable object lesson for Pacific Theater Commanders.
Because of the relative stalemate at Coral Sea, the commanding Admiral of the Pacific Theater Navy Fleet, Admiral Chester Nimitz knew that to win battles, the forces of the Pacific fleet had to be vastly increased. After Pearl Harbor there were a number of ships that were severely damaged, and Admiral Nimitz wisely moved heaven and earth to get all the Naval Assets possible ready for the eventual Battle of Midway. The Battle of the Coral Sea, while mildly successful, lent credence and a new sense of urgency to the efforts by Admiral Nimitz.