From the 250s to the 280s AD, Roman Gaul suffered a serious crisis with its fortified borders being attacked on several occasions by barbarians. Nevertheless, the situation improved in the first half of the 4th century, which was a period of revival and prosperity for Roman Gaul. In 312, Emperor Constantine I converted to Christianity. Subsequently, Christians, who had been persecuted until then, increased rapidly across the entire Roman Empire. But, from the beginning of the 5th century, the Barbarian Invasions resumed. Teutonic tribes invaded the region from present-day Germany, the Visigoths settling in the southwest, the Burgundians along the Rhine River Valley, and the Franks (from whom the French take their name) in the north.