Gaius Galerius Valerius Maximianus (; 258 – May 311) was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311. Early life Galerius was born near Serdica, in Dacia Ripensis, later named Dacia Mediterranea, though some modern scholars consider the strategic site where he later built his palace named after his mother – Felix Romuliana (Gamzigrad) – his birth and funeral place. His father was a Thracian and his mother Romula had left Roman Dacia because of the Carpians' attacks. He originally followed his father's occupation, that of a herdsman, where he was nicknamed "Armentarius", herdsman (). His original cognomen was "Maximinus", but he changed it to "Maximianus" after becoming Caesar. He served with distinction as a soldier under Emperors Aurelian and Probus, and in 293, at the establishment of the Tetrarchy, was designated Caesar along with Constantius Chlorus, receiving in marriage Diocletian's daughter Valeria (later known as Galeria Valeria), and at the same time being entrusted with the care of the Illyrian provinces. After a few years campaigning against Sarmatians and Goths on the Danube, he received command of the legions on the eastern imperial limits. Soon after his appointment, Galerius was dispatched to Egypt to fight the rebellious cities Busiris and Coptos. War with Persia Invasion, counterinvasion In 294, Narseh, a son of Shapur I, who had been passed over for the Sassanid succession, came into power in Persia. Narseh probably moved to eliminate Bahram III, a young man installed by a noble named Vahunam in the wake of Bahram II's death in 293. In early 294, Narseh sent Diocletian the customary package of gifts, but within Persia, he was destroying every trace of his immediate predecessors, erasing their names from public monuments. He sought to identify himself with the warlike reigns of Ardashir (r. 226–241) and Shapur (r. 241–272), who had sacked Roman Antioch and captured Emperor Valerian. In 295 or 296, Narseh declared war on Rome. He appears to have first invaded western Armenia, retaking the lands delivered to Tiridates in the peace of 287. He occupied the lands there until the following