On September 15, 1777, George Washington on authorisation of Congress appointed Casimir Pulaski brigadier general in Continental Army cavalry. From the article:
"That opportunity came at the Battle of Brandywine on September 11, 1777. The British caught Washington in a precarious position with a clever flanking maneuver. It appeared that the Americans might be routed and Washington captured, but Pulaski--possessing no rank--asked Washington to give him temporary command of some cavalry. Washington assented and Pulaski skillfully led a counterattack, helping delay the British enough for the Continental Army to retreat and regroup.
Shortly after Brandywine, Pulaski’s wishes were granted when he was promoted to brigadier general and given “chief command of the American light dragoons."2 Pulaski was a talented general--and more than able to effectively train horseman--but struggled with his first American command. His inability to speak English and conflicting views regarding the cavalry’s importance in the military eventually led to his resignation from the post.
Far from discouraged, Pulaski, with Washington and Congress’s approval, raised a new regiment of cavalry, along with a few regiments of infantry, which came to be known as Pulaski’s Legion. Pulaski chose many of his officers and was able to train his legion as he saw fit. They rapidly became a dangerous force as Pulaski capitalized on his experience, creating some of America’s first effective cavalry. After months of training and fighting in the northern theater, Washington sent Pulaski’s Legion to the Carolinas to help the war’s struggling southern front."