He joined the Army in 1797 and served 5 years in India with the 25th Regiment of Foot. He saw action at the Battle of Mallavelly, Siege of Seringapatam and at Doondia. At the storming of the fort of Turnioul, he volunteered and led the assault with fifty dismounted dragoons. Over the course of 3 years, he took part in the capture of more than 15 fortresses. By 1806, he was serving with the 21st Fusiliers during the Sicilian campaign, which concluded the War of the Third Coalition with the Battle of Maida. For 1807-1811, he returned to India with the 17th Light Dragoons. He returned to Europe in 1811 and joined the 18th Hussars, within the army under the Duke of Wellington. He saw action at the Battle of Toulouse and the Battle of Waterloo. He was promoted to Lieutenant-Colonel, with effect from the date of Waterloo. He married shortly afterwards and spent his time between France and Hillingdon, where he leased nearby Hayes Park House from 1829 to 1843. The extended Grant family appear several times in the autobiography of their neighbour, Anthony Trollope. Grant was promoted to Colonel in 1837 and to Major-General in 1846. He was appointed Governor of Scarborough Castle and was created Companion of The Most Honourable Order of the Bath (C.B.)