Britain had increased its cavalry reserves after seeing the effectiveness of mounted Boers during the Second Boer War (1899–1902). Horse-mounted units were used from the earliest days of World War I: on August 22, 1914, the first British shot of the war in France was fired by a cavalryman, Edward Thomas of the 4th Royal Irish Dragoon Guards, near Casteau, during a patrol in the buildup to the Battle of Mons. Within 19 days of Britain beginning mobilization for war, on August 24, 1914, the 9th Lancers, a cavalry regiment led by David Campbell, engaged German troops with a squadron of 4th Dragoon Guards against German infantry and guns. Campbell obeyed his orders to charge, although he believed the more prudent course of action would have been to fight dismounted. The charge resulted in a British loss of 250 men and 300 horses. On September 7, Campbell's troops charged again, this time towards the German 1st Guard Dragoons, another lancer cavalry regiment. In the same year, the British Household Cavalry completed their penultimate operation on horseback—the Allied retreat from Mons.