Question: Jean-Joseph Sourbader de Gimat was part of a war in Yorktown Virginia with American and French allies that ended on what date?

Context paragraphs:
Yorktown campaign: The Yorktown or Virginia campaign was a series of military maneuvers and battles during the American Revolutionary War that culminated in the decisive Siege of Yorktown in October 1781.  The result of the campaign was the surrender of the British Army force of General Charles Earl Cornwallis, an event that led directly to the beginning of serious peace negotiations and the eventual end of the war.  The campaign was marked by disagreements, indecision, and miscommunication on the part of British leaders, and by a remarkable set of cooperative decisions, at times in violation of orders, by the French and Americans.

John Stewart, Earl of Buchan: John Stewart, Earl of Buchan (c. 1381 – 17 August 1424) was a Scottish nobleman and soldier who fought alongside Scotland's French allies during the Hundred Years War.  In 1419 he was sent to France by his father the Duke of Albany, Regent of Scotland, with an army of 6,000 men.  Stewart led the combined Franco-Scottish army at the Battle of Baugé on 21 March 1421, where he comprehensively defeated the English forces, proving that the English could at last be beaten.

Siege of Yorktown: The Siege of Yorktown, also known as the Battle of Yorktown, the Surrender at Yorktown, German Battle or the Siege of Little York, ending on October 19, 1781, at Yorktown, Virginia, was a decisive victory by a combined force of American Continental Army troops led by General George Washington and French Army troops led by the Comte de Rochambeau over a British Army commanded by British peer and Lieutenant General Charles Cornwallis.  The culmination of the Yorktown campaign, the siege proved to be the last major land battle of the American Revolutionary War in the North American theater, as the surrender by Cornwallis, and the capture of both him and his army, prompted the British government to negotiate an end to the conflict.  The battle boosted faltering American morale and revived French enthusiasm for the war, as well as undermining popular support for the conflict in Great Britain.

Versailles Township: The Township of Versailles was one of the seven original townships of Allegheny County, Pennsylvania created during the first meeting of the Allegheny County Court on September 24, 1788.  The other townships included the new county’s seat Pitt (eventually known as Pittsburgh, Pennsylvania), Plum, St. Clair, Moon, Mifflin, and Elizabeth.  Versailles was named for Versailles, France, in honor of the United States' French allies during the American Revolution.

France–Poland relations: Polish–French relations date back several centuries, although they really only became relevant in the times of the French Revolution and the reign of Napoleon I.  Poles were allies of Napoleon; a large Polish community settled in France in the 19th century, and Poles and French were also allies during the interwar period.  Never in history has a Polish army fought against its French counterpart or otherwise.  Official relations, having cooled during the Cold War, have improved since the fall of communism.  Currently both countries are part of the European Union and NATO.  Poland is also an observer in the "Organisation internationale de la francophonie".

Prince Claudin: Claudin (or Claudine) is the son of the Frankish King Claudas in the Arthurian legend.  He appears in the Old French Lancelot-Grail and Thomas Malory's 15th century English work "Le Morte d'Arthur", in sections based on the French cycle.  His father is a villain during King Arthur's early reign, an enemy to Arthur's French allies Ban and Bors, but Claudin is a virtuous young man and wants no part of his father's schemes.  Claudas eventually succumbs to Arthur and company, and Claudin seeks adventure elsewhere.  He becomes one of only twelve knights to achieve the Holy Grail, along with Galahad, Bors the Younger, and Percival.

Jean-Joseph Sourbader de Gimat: Jean-Joseph Sourbader de Gimat was a volunteer French officer who served in the Continental Army during the American Revolutionary War.  Born into a military family, he entered the French royal army in 1761.  By 1776 he was a first lieutenant but went to America with Gilbert Motier, marquis de La Fayette with the promise of becoming a major.  After serving as La Fayette's aide at Brandywine, Gloucester, Barren Hill, and Monmouth, he went back to France for one year.  Returning to America in 1780, he was appointed to command a light infantry unit which fought at Green Spring in 1781.  He led his men in a successful assault at Yorktown that same year.  He returned to France in 1782 and was named colonel in command of a colonial regiment in Martinique.  He later was governor of Saint Lucia from 1789 to 1792.

Siege of Yorktown (1862): The Battle of Yorktown or Siege of Yorktown was fought from April 5 to May 4, 1862, as part of the Peninsula Campaign of the American Civil War.  Marching from Fort Monroe, Union Maj. Gen. George B. McClellan's Army of the Potomac encountered Maj. Gen. John B. Magruder's small Confederate force at Yorktown behind the Warwick Line.  McClellan suspended his march up the Peninsula toward Richmond and settled in for siege operations.

Yorktown Wrecks: The Yorktown Wrecks is an expansive archaeologically sensitive area of Virginia's York River, in whose waters significant naval remnants of the American Revolutionary War are located.  As a result of surveys conducted in the 1970s, at least nine sunken vessels sunken or scuttled around the time of the 1781 Siege of Yorktown have been identified.  In the days preceding the siege, American and French naval forces sank a number of British vessels off Yorktown, and General Charles Cornwallis ordered the scuttling of other ships.  At the end of the siege and the British surrender, at least twenty-six British vessels were unaccounted for, and are believed to lie in the York River.

Battle of the Chesapeake: The Battle of the Chesapeake, also known as the Battle of the Virginia Capes or simply the Battle of the Capes, was a crucial naval battle in the American Revolutionary War that took place near the mouth of Chesapeake Bay on 5 September 1781.  The combatants were a British fleet led by Rear Admiral Sir Thomas Graves and a French fleet led by Rear Admiral Francois Joseph Paul, the Comte de Grasse.  The battle was strategically decisive, in that it prevented the Royal Navy from reinforcing or evacuating the forces of Lieutenant General Lord Cornwallis at Yorktown, Virginia.  The French were able to achieve control of the sea lanes against the British, allowing them to provide the Franco-American army with siege artillery and French reinforcements—all of which proved decisive in the Siege of Yorktown, effectively securing independence for the Thirteen Colonies.

Supporting paragraphs: Jean-Joseph Sourbader de Gimat Siege of Yorktown
Answer: October 19, 1781