Aerial view of Asan Ridge and the War in the Pacific National Historical Park. Established in 1978, the Park is composed of various sites on the western shore of the island; it is unique in the US National Park System in that it honors all those who participated in the Pacific Theater of World War II. During the Second World War, Guam was captured by Japanese forces in 1941 and liberated by the Americans in 1944. The Park includes former battlefields, gun emplacements, trenches, caves, and historic structures. Photo courtesy of the US National Park Service.