Field Marshal John Campbell, 5th Duke of Argyll, styled Marquess of Lorne from 1761 to 1770, was a Scottish soldier and nobleman. After serving as a junior officer in Flanders during the War of the Austrian Succession, he was given command of a regiment and was redeployed to Scotland where he opposed the Jacobites at Loch Fyne at an early stage of the Jacobite Rebellion and went on to fight against them at the Battle of Falkirk Muir and then at the Battle of Culloden. He later became adjutant-general in Ireland and spent some 20 years as a Member of Parliament before retiring to Inveraray Castle.

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.