The Siege of Yorktown, also known as the Battle of Yorktown, the Surrender at Yorktown or the German Battle, 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 lord 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.

In 1780, 5,500 French soldiers landed in Rhode Island to assist their American allies in operations against British-controlled New York City. Following the arrival of dispatches from France that included the possibility of support from the French West Indies fleet of the Comte de Grasse, Washington and Rochambeau decided to ask de Grasse for assistance either in besieging New York, or in military operations against a British army operating in Virginia. On the advice of Rochambeau, de Grasse informed them of his intent to sail to the Chesapeake Bay, where Cornwallis had taken command of the army. Cornwallis, at first given confusing orders by his superior officer, Henry Clinton, was eventually ordered to build a defensible deep-water port, which he began to do at Yorktown, Virginia. Cornwallis' movements in Virginia were shadowed by a Continental Army force led by the Marquis de Lafayette.

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.

On April 5, the IV Corps of Brig. Gen. Erasmus D. Keyes made initial contact with Confederate defensive works at Lee's Mill, an area McClellan expected to move through without resistance. Magruder's ostentatious movement of troops back and forth convinced the Union that his works were strongly held. As the two armies fought an artillery duel, reconnaissance indicated to Keyes the strength and breadth of the Confederate fortifications, and he advised McClellan against assaulting them. McClellan ordered the construction of siege fortifications and brought his heavy siege guns to the front. In the meantime, Gen. Joseph E. Johnston brought reinforcements for Magruder.