The previous year ended with Severus’ forces trying to force their way through the Cilician passes in the Taurus Mountains. Initially, they were repelled by strong resistance from Niger’s troops, who were holding excellent strategic positions. However, as the siege of Niger’s positions progressed, the winter weather began to favour Severus. Heavy rainstorms and snowfall started to weaken Niger’s defences and finally Severus’ forces, who saw the weather as a form of divine intervention, managed to break through. They were now able to enter Cilicia.
The armies of Severus and Niger met at Issus, where they fought the decisive battle of the war in the East. Severus’ troops were led by his generals Valerianus and Anullinus, while Niger lead his forces in person. The battle probably took place in May, at a location that has strong historical significance: it was at Issus that Alexander the Great defeated Darius, King of the Persians, in 333 BCE. At Issus, a fierce battle ensued and Severus’ troops formed testudo to protect themselves from the missiles hurled against them by their opponents. Both armies were evenly matched and the battle turned into a bloody affair, with both sides suffering heavy casualties. In the end, violent weather may have determined the outcome of the battle. Thunder, lightning and heavy rain beat in Niger’s soldiers’ faces and his forces started to give ground. According to Cassius Dio, 20.000 of Niger’s soldiers were killed. Severus won a decisive victory. Niger tried to flee to Antiochia, but was caught and killed in the pursuit.
Severus now had complete control of the eastern provinces and one of his most important actions was to split the province of Syria into two separate provinces, Coele Syria and Phoenice, probably to prevent future Syrian governors from becoming all too powerful. Severus then punished the senators who supported Niger. There were no executions, but many of them were banished to small islands and had their property confiscated, with Dio – a contemporary of the emperor – claiming that he was “merciless in his search for money”. It is likely that some of the senators who lost their property were simply innocent, and many others merely supported Niger because he opposed Julianus, the man who had disgraced himself by buying the Empire from the praetorians.
 He may have done so a little later than 194, for instance in 197, when he returned to the East.
 Dio’s narrative places these measures immediately after the battle of Issus. If this is correct, Severus presumably punished Niger’s senatorial supporters that were actually in the East, i.e. in Syria or its neighbouring provinces. Severus would again punish supporters of Niger in 197 after having defeated his remaining rival Albinus.