The Guadalcanal Campaign, also known as the Battle of Guadalcanal and code-named Operation Watchtower, originally applying only to an operation to take the island of Tulagi, by Allied forces, was a military campaign fought between 7 August 1942 and 9 February 1943 on and around the island of Guadalcanal in the Pacific theater of World War II. It was the first major offensive by Allied forces against the Empire of Japan.