Answer: Because it lingered any hopes of victory the British may have had until that point.
Explanation:
The siege of Yorktown began on September 28. On October 14 two major British outposts fell to French and American attackers, the latter led by Washington’s aide, Alexander Hamilton. A British counterattack failed to retake them. On October 19, 1781, the defeated British troops of more than 7,000 men marched out to London. In December King George III and his ministers decided to send no more troops to America.
