Edwin returned in approximately 616 to conquer Northumbria with Rædwald's aid. Edwin, who ruled from approximately 616 to 633, was one of the last kings of the Deiran line to reign over all of Northumbria; it was Oswald of Bernicia (c. 634–642) who finally succeeded in making the merger more permanent. Oswald's brother Oswiu eventually succeeded him to the Northumbrian throne despite initial attempts on Deira's part to pull away again. Although the Bernician line ultimately became the royal line of Northumbria, a series of Derian sub-kings continued after Oswald, including Oswine (a relation of Edwin murdered by Oswiu in 651), Œthelwald (killed in battle 655), and Aldfrith (son of Oswiu, who disappeared after 664). Although both Œthelwald and Aldfrith were Oswiu's relations who may have received their sub-king status from him, both used Deira separatist sentiments to try to snatch independent rule of Deira. Ultimately, neither were successful and Oswiu's son Ecgfrith succeeded him to maintain the integrated Northumbrian line. While violent conflicts between Bernicia and Deira played a significant part in determining which line ultimately gained supremacy in Northumbria, marriage alliances also helped bind these two territories together. Æthelfrith married Edwin's sister Acha, although this marriage did little to prevent future squabbles between the brothers-in-law and their descendants. The second intermarriage was more successful, with Oswiu marrying Edwin's daughter and his own cousin Eanflæd to produce Ecgfrith, the beginning of the Northumbrian line. However, Oswiu had another relationship with an Irish woman named Fina which produced the problematic Aldfrith. In his Life and Miracles of St. Cuthbert, Bede declares that Aldfrith, known as Fland among the Irish, was illegitimate and therefore unfit to rule. Northumbria and Norse settlement The Viking invasions of the ninth century and the establishment of the Danelaw once again divided Northumbria. Although primarily recorded in the southern provinces of England, the Anglo-Saxon Chronicles (particularly the D and E recensions) provide some information on Northumbria's conflicts with Vikings in the late eighth and early ninth centuries. According to these chronicles, Viking raids began to affect Northumbria when a band attacked Lindisfarne in 793. After this initial catastrophic blow, Viking raids in Northumbria were either sporadic for much of the early ninth century or evidence of them was lost. However, in 865 the so-called Great Heathen Army landed in East Anglia and began a sustained campaign of conquest. The Great Army fought in Northumbria in 866–867,