Complex sentence: The division remained in positional warfare on the Verdun front through 1916 and 1917, and in late 1917 and 1918 participated in the fighting in the Argonne Forest.
Split into simpler sentences: The division remained involved in positional warfare on the Verdun front through 1916 and 1917. In late 1917 and 1918, it participated in the fighting in the Argonne Forest.