What was the cause of the Battle of the Coral Sea?

The Battle of Coral Sea was a four day battle that took place in May of 1942. This battle was caused by the desire of the Japanese to control the Coral Sea during World War II.  The Japanese wished to control the Coral Sea in order to strengthen their defensive positioning for the benefit of the Japanese empire in the South Pacific.  To accomplish this goal, the Japanese invaded Port Moresby in southeast New Guinea.  This promoted the Allied forces, led by the American task force, to attack these Japanese invaders with aircraft carrier planes.  The reason that the Allied forces were in the Coral Sea in time to respond to the invasion was due to the fact that Allied code-breakers were able to decode Japanese communications and learn of their plans for invading the area.  The battle is considered to be a victory for the Allied forces because it was the first time that they were able to successfully stop and major Japanese advance.  It was a tactical victory for the Japanese, however, due the the number of opposing ships that their forces were able to sink. This battle is significant because it was the first air-sea battle to take place in history.