Pierre Dominique Garnier, born 19 December 1756 – died 11 May 1827, was a French general during the French Revolutionary Wars and Napoleonic Wars.
 He enlisted in the French royal army in 1773 and served in the French West Indies.
 At the outbreak of the French Revolution he left his career as an architect and joined the National Guard.
 Continuing in the army, he enjoyed rapid promotion while fighting in several theaters during the War of the First Coalition.
 As a general of brigade he fought at Toulon and was elevated to the rank of general of division.
 After fighting at Loano in late 1795, he found himself under the command of Napoleon Bonaparte for the Montenotte Campaign in April 1796.
 Bonaparte had little use for Garnier, however.
 Garnier saw action in Italy during the War of the Second Coalition in 1799 and 1800.
 During the Napoleonic Wars he held reserve or garrison commands and retired from the military in 1816.
 His surname is one of the 660 names inscribed under the Arc de Triomphe.
The War of 1812 (18121815) was a conflict fought between the United States, the United Kingdom, and their respective allies.
 Historians in Britain often see it as a minor theater of the Napoleonic Wars; in the United States and Canada, it is seen as a war in its own right.
Maximilian, Freiherr (Baron) von Wimpffen (1770–1854) was a military commander who served in the Austrian army during the French Revolutionary Wars and Napoleonic Wars.
 Although a competent field commander, he was above all noted for his excellent knowledge of military strategy and tactics, which made him a key member in the General Staff of the Imperial and Royal Army during the Napoleonic Wars.
Thomas Biddle (November 21, 1790 – August 29, 1831) was an American military hero, during the War of 1812.
 Biddle is better known though for having been killed in a duel with Missouri Congressman Spencer Pettis.
HMS "Phoebe" was a 36-gun fifth rate of the British Royal Navy.
 She had a career of almost twenty years and fought in the French Revolutionary Wars, the Napoleonic Wars and the War of 1812.
 Overall, her crews were awarded six clasps to the Naval General Service Medals, with two taking place in the French Revolutionary Wars, three during the Napoleonic Wars and the sixth in the War of 1812.
 Three of the clasps carried the name "Phoebe".
 During her career, "Phoebe" sailed to the Mediterranean, the Baltic, the Indian Ocean, South East Asia, North America and South America.
The Illinois Campaign, also known as Clark's Northwestern Campaign (1778-1779), was a series of events during the American Revolutionary War in which a small force of Virginia militiamen, led by George Rogers Clark, seized control of several British posts in the Illinois Country, in what are now Illinois and Indiana in the Midwestern United States.
 The campaign is the best-known action of the western theater of the war and the source of Clark's reputation as an early American military hero.
Admiral Sir Richard Lee KCB KTS (c. 1765 – 5 August 1837) was a prominent officer of the British Royal Navy who served in the American Revolutionary War, the French Revolutionary Wars and the Napoleonic Wars.
 His early career was marked by his participation in a number of important battles during the American war, during the French Revolutionary Wars he spent an unremarkable period of time in the Caribbean, but during the Napoleonic Wars he was again prominent, participating heavily in a number of important engagements.
 In 1812 Lee was promoted to rear-admiral and was unable to get an appointment, his future as a serving officer in doubt.
 Although he never again served in an active capacity, he continued to receive promotions and rewards for his lengthy service, both from the British and Portuguese royal families.
 He died at his home in Walmer, Kent in 1837 at the age of 72 as a full admiral.
Michael V. Leggiere is a professor of history who works at the University of North Texas as deputy-director for the Barsanti Center for Military History.
 Leggiere's emphasis is on the Napoleonic era, and he deals most specifically with Prussian operations in Germany and France during 1813-14.
 According to his university profile, Leggiere is "one of the leading historians in the world of the Napoleonic Wars."
 This is supported by the fact that Leggiere has received the International Napoleonic Society Literary Award two times, once in 2002 and again in 2007.
 Leggiere also serves on the program committee of the Society for Military History and is on the board of directors for the Consortium on Revolutionary Europe.
Sir Thomas Baker KCB, KWN (1771 – 26 January 1845) was an officer of the Royal Navy, who saw service during the American War of Independence, and the French Revolutionary and Napoleonic Wars.
 He had obtained his own command during the French Revolutionary Wars and was to play a part in bringing about three of the battles of the Napoleonic Wars, the Battle of Copenhagen, the Battle of Trafalgar, and the Battle of Cape Ortegal.
 He only directly participated in the third, but his actions there, and the capture of the French frigate "Didon" (1805) beforehand brought him honours and rewards.
 While towing the "Didon" to a British port, he and another vessel were sighted by the combined Franco-Spanish fleet under Pierre-Charles Villeneuve, and mistaken as scouts for the Channel Fleet.
 He therefore turned south to Cadiz, leading to the abandonment of the planned invasion of England, and the destruction of the French fleet at Trafalgar by Horatio Nelson some months later.
 He rose through the ranks after the end of the wars with France, and was commander of the South American station during Charles Darwin's voyage aboard  .
 He eventually died with the rank of vice-admiral in 1845 after a long and distinguished career.
Captain James Robert Mosse (1745–1801) was a British naval officer and military hero killed during his command at the Battle of Copenhagen during the Napoleonic Wars.

Question: Who killed an American military hero during the war which historians in Britain see as a minor theater of the Napoleonic Wars?
Answer: Spencer Pettis