Emperor Constantius returned to Britain in 306, despite his poor health, with an army aiming to invade northern Britain, the provincial defences having been rebuilt in the preceding years. Little is known of his campaigns with scant archaeological evidence, but fragmentary historical sources suggest he reached the far north of Britain and won a major battle in early summer before returning south. His son Constantine (later Constantine the Great) spent a year in northern Britain at his father's side, campaigning against the Picts beyond Hadrian's Wall in the summer and autumn. Constantius died in York in July 306 with his son at his side. Constantine then successfully used Britain as the starting point of his march to the imperial throne, unlike the earlier usurper, Albinus.