Kaleb, also known as Saint Elesbaan, was King of Aksum, which was situated in modern-day Eritrea and Northern Ethiopia. Kaleb invaded Yemen around 520, to overthrow Dhu Nuwas, a Jew who was persecuting the Christian community of Najran. After much fighting, Kaleb's soldiers eventually routed Yusuf's forces and killed the king, allowing Kaleb to appoint Sumuafa' Ashawa', a native Christian (named Esimiphaios by Procopius), as his viceroy of Himyar.
As a result of his protection of the Christians, Kaleb is known as Saint Elesbaan after the sixteenth-century Cardinal Caesar Baronius added him to his edition of the Roman Martyrology despite his being a miaphysite. However, the Catholic Church now recognises that Miaphysitism — the actual Christology of Oriental Orthodoxy — is not heretical as signed agreements between the Popes and various Patriarchs confirm.