Why was it a mistake for Gen. Cornwallis to camp his army at Yorktown?

Yorktown’s position on a peninsula made it vulnerable: American and French forces could surround the British army by land, while the French fleet blocked escape and resupply by sea. That left Cornwallis trapped and ultimately forced him to surrender. So the key mistake was camping at a place where his army could be surrounded, not simply that supplies were difficult to obtain.

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