Field Marshal Colin Campbell, 1st Baron Clyde,, was a British Army officer. After serving in the Peninsular War and the War of 1812, he commanded the 98th Regiment of Foot during the First Opium War and then commanded a brigade during the Second Anglo-Sikh War. He went on to command the Highland Brigade at the Battle of Alma and with his "thin red line of Highlanders" he repulsed the Russian attack on Balaclava during the Crimean War. At an early stage of the Indian Mutiny, he became Commander-in-Chief, India and, in that role, he relieved and then evacuated Lucknow and, after attacking and decisively defeating Tatya Tope at the Second Battle of Cawnpore, captured Lucknow again. Whilst still commander-in-chief he dealt with the "White Mutiny" among East India Company troops, and organised the army sent east in the Second Opium War.

Field marshal (FM) has been the highest rank in the British Army since 1736. A five-star rank with NATO code OF-10, it is equivalent to an Admiral of the Fleet in the Royal Navy or a Marshal of the Royal Air Force in the Royal Air Force (RAF). A Field Marshal's insignia consists of two crossed batons surrounded by yellow leaves below the Tudor Crown. Like Marshals of the Royal Air Force and Admirals of the Fleet, Field Marshals traditionally remain officers for life, though on half-pay when not in an appointment or retired. The rank has been used sporadically throughout its history, and was vacant during parts of the 18th and 19th centuries. After the Second World War, it became standard practice to appoint the Chief of the Imperial General Staff to the rank on his last day in the post. Army officers occupying the post of Chief of the Defence Staff, the professional head of all the British Armed Forces, were usually promoted to the rank upon their appointment.