Hill 40 is located in Guam

Hill 40 is a militarily historic landform on the island of Guam. It is located about 325 metres (1,066 ft) east of Bangi Point, south of Agat on the island's west coast, rising to a height of 40 to 60 feet (12 to 18 m) above the coastal plain, with a strategically significant view of the Agat Invasion Beach. This hill was the scene of some of the most intense fighting during the landing phase of the 1944 Battle of Guam as Allied forces sought to establish their beachhead against the defending Japanese forces. The American 4th Marine Regiment of the 1st Provisional Marine Brigade captured Hill 40 on June 21, 1944, the day of the landing. That night the Japanese launched a counteroffensive that successfully retook the hill. The Marines regrouped and regained the hill, and held off a second counterattack. The Japanese 38th Regiment was wiped out by this military action.

• http://en.wikipedia.org/wiki/Hill 40