But, notwithstanding the union by marriage between the families, the rivalry between Mercia and Northumbria could not be allayed; it must be decided on the battlefield. It was only when driven to desperation by the encroachments and insults of Penda, that Oswy resolved to engage in a final conflict with the man who had defeated and slain his two predecessors, Edwin and Oswald. During the thirteen years that had elapsed since the overthrow of Oswald, Penda had periodically subjected Northumbria to frightful devastations. Oswy, knowing his weakness, when the eighty-year-old pagan had got as far north as Bamborough, entreated for peace, and sent him a present of all the jewels and treasures of which he could dispose. Penda set them aside roughly, resolved, so it was believed, to root out and destroy the whole Northumbrian people. Then, in his despair, Oswy vowed—should God strengthen his hand and lead him to victory—that he would give his infant daughter to God and endow twelve monasteries. “Since the pagan will not take our gifts,” he said, “let us offer them to One who will.” The battle of Winwaed resulted in the complete rout of the Mercians and their wholesale destruction, and Penda himself fell. For the moment the ruin of Mercia seemed complete, and Oswy extended his supremacy over the whole of it. For three years the Mercians endured this foreign rule; but in 659 they surged up in revolt, drove the Northumbrian thanes from the land, and raised Wulfhere, a younger son of Penda, to the throne. Under the able arm of this new king Mercia rose once more into a power even greater than that under Penda. Oswy died in 670, and thenceforth no Northumbrian king made any attempt to obtain the dominion over the Mid or Southern English. During the three years after the death of Penda, Oswy had poured missionaries into Mercia. Peada had already brought the Irish monk Diuma with him, and he became bishop in Mercia. He was followed by another Irishman, Ceolach, a disciple of S. Columba. The third bishop was Trumhere, a Northumbrian abbot, consecrated at Lindisfarne. His successors, Jaruman and Ceadda, had also been ordained by the Scots. In 658 Wulfhere had married Ermenilda, daughter of Ercombert, King of Kent, and of his wife S. Sexburga. This was just before the revolt which raised him to the throne. He does not seem to have been a Christian like his brother Peada, but to have felt much like old Penda, his father. By her he had four children—Werburga, Ceonred, Rufinus, and Wulfhad.