Umbar (Q. ‘Fate’) was a coastal area in Harad located seventy leagues south of the river Harnen. It consisted of a cape, firth, havens, and a fortress. First settled by Númenoreans returning to Middle-earth in the later Second Age, it became their chief haven outside their own land, and it was here that Ar-Pharazôn contested the power of Sauron in SA 3261.
After the kingdom fell into moral decline, Umbar became a fortress of the King’s Men (later called the Black Númenoreans). It proved a mighty fortress nonetheless, rapidly becoming a centre of Númenor’s sea power.
Following the Downfall of Númenor, the Faithful who had survived went on to construct their own realms of Arnor and Gondor to the North of Umbar – and so rivalry grew between the Faithful and the Dúnedain of Umbar. During the Third Age, Gondor and the Corsairs of Umbar were frequently at war with one another, and the southern realm changed hands numerous times.
During the War of the Ring, a large corsair fleet attacked Pelargir, but was defeated by Aragorn and the army of the Dead; by the Fouth Age, Umbar was once again under Gondor’s control.