The Arbuthnot and Ambrister incident occurred in 1818 during the First Seminole War. American General Andrew Jackson invaded Spanish Florida and captured and executed Alexander George Arbuthnot and Robert C. Ambrister, two British subjects charged with aiding Seminole and Creek Indians against the United States. Arbuthnot and Armbrister were tried and executed in Bay County, Florida near what continues to be called Court Martial Lake. Jackson's actions triggered short-lived protests from the British and Spanish governments and an investigation by the United States Congress. Congressional reports found fault with Jackson's handling of the trial and execution of Arbuthnot and Armbrister, but Congress chose not to censure the popular general.
Robert Chrystie Armbrister (1797–1818) was a British subject and a native of Nassau in the Bahamas. Armbrister was the youngest son of the South Carolina-born Loyalist, James Armbrister (1757/58-1833), who was then a lieutenant colonel in the colonial militia of the Bahamas. Son Robert had served in the British Royal Navy as a volunteer and as a midshipman between 1809 and 1813, when he returned to the Bahamas. During 1814-1815, he served in the Spanish Floridas as an auxiliary 2nd lieutenant of the British Corps of Colonial Marines, commanded by Brevet Major Edward Nicolls of the Royal Marines. Discharged from the military in Nassau in 1815, the former Marine lieutenant returned to Spanish Florida in 1817 with his fellow former Marine, Captain George Woodbine, and the Scottish soldier of fortune Gregor MacGregor.
Alexander (George) Arbuthnot (born in Montrose, Scotland, in 1748) was an older man, a Scottish merchant, translator, and diplomatic go-between, on occasion, who had been present in the Floridas since 1803. The executions of Arbuthnot, Armbrister, and at least two prominent Creek-Seminole leaders upon the demonstrated instructions of General Jackson, was perceived as an act of barbarity outside the existing conventions of warfare, both in Great Britain and elsewhere beyond the confines of the United States.