Young Ellis became a lieutenant in the 41st Foot in 1792, and captain in the 23rd Fusiliers on 20 January 1796. Joining the Fusiliers, a boy-captain of barely fourteen, he served with it in the descent on Ostend in 1798, in the 1799 Anglo-Russian invasion of Holland (wounded), in the Channel, at Ferrol and in the Mediterranean in 1800, in Egypt in 1801 (wounded, gold medal and rank of major), in Hanover in 1805, and at Copenhagen in 1807. A youthful veteran of twenty-five, he succeeded to the command of the first battalion of his regiment, without purchase, in Nova Scotia in 1808, and commanded it in the expedition against Martinique in 1809, where at the siege of Fort Bourbon he offered to take the flints out of his men's firelocks and carry the works with his fusiliers at the point of the bayonet, an enterprise which the commander-in-chief, Sir George Beckwith, refused to sanction.