Pinckney participated in the 1780 defense of Charleston against British siege but the city fell. Major General Lincoln surrendered his 5,000 men to the British on May 12, 1780, and Pinckney became a prisoner of war. As such, he demonstrated leadership, playing a major role in maintaining the troops' loyalty to the Patriots' cause. During this time, he said, "If I had a vein that did not beat with the love of my Country, I myself would open it. If I had a drop of blood that could flow dishonorable, I myself would let it out." He was kept in close confinement until his release in 1782. In November 1783, he was commissioned a brevet Brigadier General in the Continental Army shortly before the southern regiments were disbanded. He was promoted to Major General during his subsequent service in the South Carolina militia.