1733–March 1785
Sumner represented Bute County in the North Carolina Provincial Congress that met in August–September 1775 and elected him a major of the minutemen of Halifax County. In November he marched to the aid of the Virginians near Norfolk. After his election by the North Carolina Provincial Congress as colonel of the Third Regiment of North Carolina Continentals, he went to the Lower Cape Fear and from there to Charleston, S.C., where in June 1776 he and his troops assisted in that town's defense against the British. Later he joined Major General Charles Lee, commanding general of the Southern Department, on a projected expedition against Florida, but in September he left the troops in Savannah to return to North Carolina for supplies. The following spring he led his regiment north and joined General George Washington's army at Morristown, N.J. He and his regiment served with Washington through the Battles of Brandywine and Germantown and endured the terrible winter at Valley Forge. Illness in the spring of 1778 forced Sumner to return to North Carolina. During the summer he recruited for the North Carolina Continental regiments.
The Continental Congress elected Sumner brigadier general on January 9, 1779. The next spring he led a brigade of newly recruited Continentals to South Carolina, where he commanded the right wing of the assault on the enemy troops at the Battle of Stono Ferry on June 20th. Afterwards he fell into a "low state of Health" and returned to North Carolina, where for more than a year he recruited for the North Carolina regiments. He then was named commanding general of a brigade of militia that he marched to the southern part of the state to aid in the defense against an invasion by Lord Cornwallis. In October, angered at the state legislature's appointment of Brigadier General William Smallwood of Maryland to the command of the state troops, Sumner refused further militia duty. When Nathanael Greene came south in December 1780 to assume command of the Southern Department, he sought Sumner's help in the rehabilitation of the North Carolina Continentals. Sumner recruited in North Carolina until June 2, 1781, when he was ordered to join Greene in South Carolina; shortly after 1 August he reached the Southern army with three small regiments of 350 raw Continentals. On September 8th, Sumner's brigades were stationed on the right of the second line at the Battle of Eutaw Springs, where they fought well. During the remainder of the war Sumner was in charge of military forces in North Carolina.
In 1783 he returned to his tavern keeping, his plantation, and his three minor children. On April 18th he presided over the meeting of the North Carolina Society of the Cincinnati at Hillsborough as the first president of that organization. He died at his home in Warren County sometime between the 15th and 19th of March 1785. At the time of his death he owned 20,000 acres of land and enslaved thirty-four people.