Complex sentence: Clausewitz's unit fought at Wavre (18--19 June 1815), preventing large reinforcements from reaching Napoleon at Waterloo director of the "Kriegsakademie", where he served until 1830.
Split into simpler sentences: Clausewitz's unit fought at Wavre (18--19 June 1815), preventing large reinforcements from reaching Napoleon at Waterloo. After the war Clausewitz served as the director of the "Kriegsakademie", where he served until 1830.