The 43rd was one of the earliest arrivals in Spain when the Peninsular War broke out, and Brown was with his regiment at Vimeiro, and in the Corunna retreat.

[1] The 85th was next employed under General Robert Ross in America, and Brown, who received a severe wound at the action of Bladensburg, was promoted to a lieutenant colonelcy.

He was made a colonel and Knight of the Royal Guelphic Order in 1831, and by 1852 had arrived at the rank of lieutenant general and the dignity of Knight Commander of the Order of the Bath In 1850 he was appointed Adjutant-General to the Forces,[2] but following the appointment of Lord Hardinge to the post of commander-in-chief, Brown left the Horse Guards in 1853.

[1] In 1854, on the despatch of a British force to the East, Sir George Brown was appointed to command the Light Division.

This he led in action, and administered in camp, on Peninsular principles, and, whilst preserving the strictest discipline to a degree which came in for criticism, he made himself beloved by his men.