Badly wounded during the Peninsular campaign, Campbell was rewarded with a knighthood and a baronetcy, later holding a number of prestigious military commands.

In 1781 the 97th was ordered aboard ships of the Channel Fleet for service as temporary Royal Marines and Campbell served at the Great Siege of Gibraltar and the Battle of Dogger Bank against the Dutch in the same year.

[1] In India Campbell rose rapidly through the ranks and by 1795 was a lieutenant colonel, serving in the Fourth Anglo-Mysore War in 1799 under General Sir Arthur Wellesley and participating in the Battle of Seringapatam that concluded the campaign.

In the aftermath of the victory, Campbell was detached from his regiment and served in a number of military administration posts in Southern India, including governor of Seringapatam in 1805.

[1] Campbell was appointed brigadier general and was stationed in Ireland, before joining Wellesley's army in Portugal during the Peninsular War in January 1809.

The elder son, Lieutenant John Morshead Campbell was killed at the Battle of Assaye in 1803 during the Second Anglo-Maratha War,{{efn|Stuart Reid in the ODNB states "Lieutenant John Morshead Campbell, was killed in action at Assaye in 1804" but the year is probably wrong as the Battle of Assaye was fought in 1803 and Charles Mosley states that the death occurred in 1803[citation needed] and the younger Major Allan William Campbell died of his wounds at Pamplona on 9 October 1813 having been wounded at the battle of Sorauren whilst attached to the Portuguese army during the Peninsular War.