Their column was immediately hit by heavy concentrated fire from 75-mm and 105-m artillery, tanks, mortars and heavy small-arms and machine guns. The Marines returned fire and after two hours, the Marines managed to destroy two of the 75 mm guns, one Japanese tank, and several machine-gun nests. Recognizing the Japanese held the advantage in terrain and cover, the Marines withdrew their forces back. Later it was determined that the attack was against a full Japanese battalion of "Rikusentai", the elite Special Naval Landing Force. Guam was finally declared secured on 10 August 1944, after an intense three-week battle.