He served in the Peninsular War and then the Hundred Days, fighting at the Battle of Waterloo and taking part in an important charge led by Sir John Colborne against the Imperial Guard when he was wounded.

Rowan returned to Canada as Commander-in-Chief, North America in which role he made an important conciliatory speech in response to the burning of the Parliament Buildings in Montreal by an angry mob in April 1849.

[7] During the Peninsular War he fought in Spain under General Robert Craufurd: although heavily engaged providing covering fire for Sir John Moore's famous retreat, he was not present at the Battle of Corunna in January 1809, having been detached to Vigo, from where he returned to England.

[9][10] Rowan's promotion to brevet major was directly in recognition of his personal bravery and the success of his command in the fighting in the marsh which actually decided the Battle of Orthez in Wellington's favour.

[9] In this role he made an important conciliatory speech in response to the burning of the Parliament Buildings in Montreal by an angry mob in April 1849.

[20] Promoted to substantive rank of lieutenant-general on 20 January 1854,[21] Rowan returned to England in 1855 and retired to a house in Gay Street, Bath.