João I ruled until his death around 1506 and was succeeded by his son Afonso Mvemba a Nzinga. He faced a serious challenge from a half brother, Mpanzu a Kitima. The king overcame his brother in a battle waged at Mbanza Kongo. According to Afonso's own account, sent to Portugal in 1506, he was able to win the battle thanks to the intervention of a heavenly vision of Saint James and the Virgin Mary. Inspired by these events, he subsequently designed a coat of arms for Kongo that was used by all following kings on official documents, royal paraphernalia and the like until 1860. While King João I later reverted to his traditional beliefs, Afonso I established Christianity as the state religion of his kingdom.