The Battle of Unsan was a series of engagements of the Korean War that took place from 25 October to 4 November 1950 near Unsan, North Pyongan province in present-day North Korea. As part of the People's Republic of China's First Phase Campaign, the People's Volunteer Army (PVA) made repeated attacks against the Republic of Korea Army (ROK) 1st Infantry Division near Unsan beginning on 25 October, in an attempt to take advancing United Nations Command (UNC) forces by surprise. In an encounter with the United States military, the PVA 39th Corps attacked the unprepared U.S. 8th Cavalry Regiment in Unsan on 1 November, resulting in one of the most devastating U.S. losses of the war.