Explanation:Siege of Yorktown and preliminaries beginning with Arnold's Raid
In May 1781, French Admiral de Barras arrived in Rhode Island to take command of the blockaded fleet there and brought word that de Grasse would be bringing the long-awaited French fleet later in the year. Gen. George Washington met with French Lt. Gen. Rochambeau to plan operations up to and after de Grasse arrived. They decided to operate around New York City where Lt. General Henry Clinton was located, although Washington feared that Maj. Gen. Nathanael Greene could not keep Lt. Gen. Charles Cornwallis occupied in the Carolinas and would soon move into Virginia in an effort to link up with Clinton.
As a matter of fact, following the loss of his light infantry and cavalry at the Battle of Cowpens on January 17, 1781, burning his baggage train in pursuit of Greene later that month and a costly victory at the Battle of Guilford Courthouse, Cornwallis abandoned the Carolinas in May 1781. He arrived in Petersburg Virginia later that month and soon received reinforcements from Clinton, which increased his force to around 7,000 men.
Cornwallis spent the next couple of months maneuvering against the Maquis de Lafayette in an effort to destroy the Frenchman's roving force, but aside from a few raids in the countryside, Cornwallis was unable to carry out his objective. He also was also receiving conflicting orders from Clinton, so he now moved to establish a fort on the James River Peninsula at Yorktown as well as across the river at Gloucester. His fortifications were ready by August 22, 1781.
Meanwhile, Washington received word that Admiral de Grasse was on his way to the Chesapeake Bay area. Washington immediately abandoned his operations around New York and while decoying Clinton like he was preparing to attack various coastal positions around New York began marching south for Virginia in late August. While Washington was marching through Philadelphia, Clinton finally learned that Washington was heading south, but he was not alarmed because of the perceived superiority of the British fleet.
Long before Washington arrived at Yorktown, the French Navy had established control of the Chesapeake. The British Navy arrived first in late August, but left when they found the waters empty. The next day, de Grasse arrived and began landing forces from the West Indies. The British fleet returned and de Grasse engaged them. The 2 fleets drifted south before the French broke off. When de Grasse returned to the Chesapeake, he found that Adm. de Barras had arrived from Rhode Island. All the naval action had taken place before mid-September arrived.
Washington arrived at the end of the month. After maneuvering and an action at Gloucester, official siege operations began on October 9, 1781. Cornwallis attempted to hold out until reinforcements arrived from Clinton. However, on October 17, he could no longer hold out and a parley was called. Terms of Surrender were negotiated on October 18 and the official surrender ceremony took place without Cornwallis, who claimed illness, on October 20, 1781. Yorktown turned out to be the last major engagement of the American Revolutionary War.