Campbell returned to Britain in 1810 and in 1811 was seconded as a colonel in the Portuguese infantry, a post he held until 1813. In that year he was sent as a British military attaché to accompany the Russian Army. He was with the Russians when they invaded France in 1814. Campbell actively participated in fighting the French. He was severely wounded on 25 March 1814 while leading a cavalry charge during the Battle of Fère-Champenoise when a Russian Cossack mistook him for a French officer. Later in 1814, Campbell became a full colonel and in 1815 received a knighthood.