After service in Holland in 1799 he was part of the 1807 Copenhagen Expedition. Present at four engagements during the Walcheren Campaign, he subsequently served under Sir John Moore during the 1809 retreat from Corunna. Sandham campaigned in Holland, Flanders and France during 1814 before commanding a Brigade of the Royal Artillery at the Battle of Waterloo on 18June 1815. During the battle, his Brigade were armed with five 9-pounder cannons and one 5 1/2" howitzer. Sources claim that "the first shot fired by the allied artillery at Waterloo was fired by Sandham's brigade."