Final answer:
The decisive factor in the Battle of Yorktown was the involvement of French forces.
Step-by-step explanation:
The decisive factor in the Battle of Yorktown was the involvement of French forces. The French army, led by General Rochambeau, played a crucial role in defeating British General Cornwallis and capturing his troops. The French navy also played a key role by blocking the British fleet from providing supplies or reinforcement to Cornwallis.
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