The military conquests were partially terminated between 638 and 639 during the years of great famine in Arabia and plague in the Levant. During his reign the Levant, Egypt, Cyrenaica, Tripolitania, Fezzan, Eastern Anatolia, almost the whole of the Sassanid Persian Empire including Bactria, Persia, Azerbaijan, Armenia, Caucasus and Makran were annexed to the Rashidun Caliphate. According to one estimate more than 4,050 cities were captured during these military conquests. Prior to his death in 644, Omar had ceased all military expeditions apparently to consolidate his rule in recently conquered Roman Egypt and the newly conquered Sassanid Empire (642-644). At his death in November 644, his rule extended from present day Libya in the west to the Indus river in the east and the Oxus river in the north.