Complex sentence: During the battle the 5th Division was outnumbered by a combined force of three North Vietnamese and Viet Cong divisions resulting in the most protracted conflict of the whole 1972 Easter Offensive.
Split into simpler sentences: During the battle, the 5th Division was outnumbered by a combined force consisting of three North Vietnamese and Viet Cong divisions. This fighting which ensued became the most protracted conflict of the 1972 Easter Offensive.