Khuzestan Central Persia Caucasus Pars Khorasan Other geographies The Battle of Nahavand (Arabic: معركة نهاوند Maʿrakah Nahāwand, Persian: نبرد نهاوند Nabard-e Nahâvand), also spelled Nihavand or Nahawand, was fought in 642 between the Rashidun Muslim forces under caliph Umar and Sasanian Persian armies under King Yazdegerd III.

Under the first two caliphs Abu Bakr and Umar, Islam expanded into Palestine and Mesopotamia where it respectively confronted the East Roman and Persian (Sāsānian) empires.

According to a different version, the Arab commander Nuʿmān was able to outmaneuver his Sāsānian counterpart Fīrūzan through the use of superior tactics rather than misleading rumors.

This would not normally have been a strategy favored by the loosely disciplined Sāsānian forces; drawn from decentralized sources and led by an alliance of feudal nobles.

During the Sāsānian pursuit Fīrūzan found his horsemen caught in extended order across a rough landscape and narrow passes.

The highly motivated and well-mounted Muslims then rallied and counterattacked, inflicting very heavy losses on the disorganized Persians.

According to non-Muslim sources, Yazdegerd failed to rally enough support in Eastern Persia where the Sasanians were unpopular with the local population.

[14] Muslim sources, such as Tabari, reported that the province of Khorasan revolted against Sasanian rule, just as it had years earlier when the population had sided with Khosrau II's uncle Vistahm.