An important allied victory that stopped the japanese advance on australia was the

The correct answer was the Battle of the Coral Sea. It lasted four days from the fourth to the eighth of May 1942. It was a battle between the Japanese and the US and Australia. Australia and the US were allied.  

The Battle of the Coral Sea fought during 4–8 May 1942, was a major naval battle in the Pacific Theater of World War II between the Imperial Japanese Navy (IJN) and naval and air forces from the Unit. Although a tactical victory for the Japanese in terms of ships sunk, the battle would prove to be a strategic victory for the Allies for several reasons. The battle marked the first time since the start of the war that a major Japanese advance had been checked by the Allies