Complex sentence: To protect this important area South Vietnam had a single division in Binh Long Province, the ARVN 5th Division, which during the battle was outnumbered by a combined force of three North Vietnamese and Viet Cong divisions.
Split into simpler sentences: To protect this important area South Vietnam had a single division in Binh Long Province, the ARVN 5th Division. During the battle the outnumbered South Vietnamese battled a combined force of three North Vietnamese and Viet Cong Divisions.