Sometime after 633 Penda killed two East Anglian kings, Sigebert and Egric, in battle. He set up a vassal king in East Anglia. About 635 Penda's brother Eowa became a king in Mercia along with Penda. Possibly he ruled northern Mercia while Penda ruled in the south. In Cadwallon, Penda's ally, was defeated and killed by King Oswald of Northumbria. The armies of Oswald and Penda met in 641 at Maserfelth (later called Oswestry in Shropshire). What events led to the battle is not recorded. Penda defeated and killed Oswald. This left Penda the most powerful king in England. Nothing indicates that Penda claimed to be overlord however. In 643 Cenwalh succeeded Cynegils as king of Wessex. Cenwalh married a sister of Penda of Mercia. But in 645 when Cenwalh her (set her aside) in favor of another wife, Penda invaded Wessex. Penda drove Cenwalh into exile in East Anglia. While in exile, Wulfhere, the son of Penda, took a great deal of territory away from Wessex. He gave the Isle of Wight to Aethelwalh, King of Sussex. Cenwalh returned to his kingdom . In 650, possibly to teach him a lesson for sheltering Cenwalh, Penda drove King Anna of East Anglia out of his kingdom. Penda killed Anna in battle in .