Final answer:
General Nathanael Greene was sent by Washington to lead Cornwallis on a chase through the southern backcountry, leading to British exhaustion and a pivotal American victory at Yorktown.
Step-by-step explanation:
The person sent by Washington in 1780 to slow Cornwallis by leading him on an exhausting chase throughout the southern backcountry was General Nathanael Greene. General Greene adopted a strategy of strategic retreats and guerrilla tactics rather than direct engagement.
With limited resources, Greene knew that he could not withstand a head-on battle with British forces. Instead, he focused on a war of attrition, keeping his army mobile and in the field, thus frustrating and depleting Cornwallis's troops. This ultimately led to General Cornwallis abandoning his strategy in South Carolina and deciding to chase Greene's army, a move that stretched his supply lines thin and weakened his forces.
Cornwallis's pursuit of Greene built up to the Battle of Guilford Courthouse, where despite a British tactical victory, the cost was so high that it weakened Cornwallis's army significantly. These events were pivotal, enabling the final American victory at Yorktown, Virginia. At Yorktown, General George Washington, with the support of French allies both on land and at sea, managed to surround Cornwallis's forces, which led to the British surrender and effectively ended the American Revolutionary War.