Corsairs:

Many of the Corsairs were originally Black Númenoreans, who followed Sauron. The Corsairs of Umbar were a long-time scourge of Gondor, attacking the coastal towns and the harbors such as Pelargir. The sails of the ships were black and the Corsairs used slave labour, many of whom had been captured in Gondor, to aid the propulsion of their ships. Their main harbor was most likely Umbar, as they were known as "The Corsairs of Umbar". Their number was reduced by Thorongil in the later years of the Third Age and their last recorded attack was in the War of the Ring, where they were forstalled by Aragorn and the Grey Company along with the Dead Men of Dunharrow.