Complex sentence: Leaving a handful of light troops to oppose the French advanced post (or flank guard) on the Schortau hill, the Prussian army broke camp and moved--half an hour after the king gave the order--to attack the enemy.
Split into simpler sentences: Leaving a handful of light troops to oppose the French advanced post, the flank guard on the Schortau hill, the Prussian army broke camp and moved. A half an hour after the king gave the order they attacked the enemy.