From their heartland, the Franks gradually conquered most of Roman Gaul north of the Loire valley and east of Visigothic Aquitaine. At first they helped defend the border as allies; for example, when a major invasion of mostly East Germanic tribes crossed the Rhine in 406, the Franks fought against these invaders. In the region of Paris, Roman control persisted until 486, a decade after the fall of the emperors of Ravenna, in part due to alliances with the Franks.