Final answer:
The French troops helped defeat British forces at Yorktown in the Battle of Yorktown during the American Revolutionary War.
Step-by-step explanation:
The foreign troops who helped defeat British forces at Yorktown were the French troops. They played a crucial role in the Battle of Yorktown during the American Revolutionary War. Under the command of General Jean-Baptiste de Rochambeau, the French forces provided additional manpower, artillery, and naval support to the American forces led by General George Washington. Together, they were able to successfully siege and defeat the British army, which ultimately led to the end of the war.
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