He served with distinction during the American War of Independence, commanding a brigade of Foot Guards as part of the army of Charles Cornwallis and was wounded during the Battle of Guilford Courthouse.

He offered the British surrender during the siege of Yorktown on behalf of his superior Charles Cornwallis and is depicted in the eponymous painting by John Trumbull.

[1] On 25 July 1766, O'Hara was appointed commandant of the Africa Corps in Senegal, a colony which had been captured from France in 1758, with the rank of lieutenant colonel.

This unit was made up of British military prisoners pardoned in exchange for accepting life service in Africa.

Lt. Gen. Henry Clinton, commander of the British army in America, gave him that assignment as the French fleet under Admiral d'Estaing threatened New York City.

During Cornwallis' pursuit of Major General Nathanael Greene to the Dan River, O'Hara distinguished himself at Cowan's Ford, North Carolina on 1 February 1781.

General O'Hara represented the British at the surrender of Yorktown on 19 October 1781, as Cornwallis' adjutant, when the latter pleaded illness.

He first attempted to surrender to French Comte de Rochambeau, who declined his sword and deferred to General George Washington.

However, in what is generally regarded as the definitive modern study of the Yorktown campaign, The Guns of Independence (2005), U.S. National Park Service historian Jerome S. Greene writes simply that O'Hara extended Cornwallis's sword and, "Washington took the sword, symbolically held it a moment, and then returned it to O'Hara.

On the tenth of the same month, Napoleon marched to the siege of Toulon, to retake the hill of Arènes of which Anglo-Neapolitan forces had momentarily taken possession.

St Vincent, who was admiral in charge of the Mediterranean Fleet, recommended that the Royal Navy Victualling Yard be relocated to the Rosia Bay area, just south of the New Mole.

Governor O'Hara did not approve of St Vincent's plan as he proposed to finance it by selling the naval stores at Waterport and Irish Town.

In the Roland Emmerich film The Patriot starring Mel Gibson, Charles O'Hara was played by Peter Woodward.