After a brief peace early in Diocletian's reign, the Persians renew hostilities when they invade Armenia and defeat he Romans outside Carrhae in either 296 or 297.

However, Galerius crushes the Persians in the Battle of Satala in 298, capturing the treasury and the royal harem, an utter disgrace for the Persian monarch.

The resulting peace settlement gives the Romans control of the area between the Tigris and the Greater Zab.

This is the most decisive Roman victory for many decades; all the territories that had been lost, all the debatable lands, and control of Armenia lies in Roman hands.