The battle for the island of Guadalcanal was won by American forces on this date in 1943. See The New York Times article: Guadalcanal Is Ours from which the following is taken:
The conquest of this island, or specifically a few square miles of territory around Henderson Airfield on its northern shore, gives American forces undisputed possession both of the airfield and an excellent harbor near by, which becomes a threat to Japan’s major bases in the South Pacific.