Answer:
The French military aid.
Step-by-step explanation:
The Battle of Yorktown is one of the most important factors for the final success of the Americans against the Britishers. This battle gave the final push for the American soldiers in their demand for independence from the colonial rule of the British monarchy.
Towards the end of the Revolutionary War, most of the American states like New York City and South Carolina were already captured by the British soldiers under the leadership of General Henry Clinton and General Lord Charles Cornwallis. But with the arrival of the French soldiers under Comte de Rochambeau helped turn the tide. The plan to deceive General Clinton in believing that the French armies will attack New York where he is, the attack was in reality attacking Cornwallis in the South. So, with this plan and the help of the French fleet, the Americans successfully defeated the British in the battle of Yorktown.