South Arabia, in particular Najran, was the scene of many political, social, and religious events before the king of Aksum, Kaleb Ella Asbeḥa, gained the justification he needed to launch a large-scale attack with Byzantine support. The justification was that Yūsuf dhū Nuwās persecuted Christians in southern Arabia. This attack began in 525 AD and ended with the death of Yūsuf dhū Nuwās and the occupation of a large part of southern Arabia by Abyssinian forces under the so-called Second Abyssinian Occupation. This paper aims to shed light on the factors that prompted the Abyssinian King Kaleb to launch this campaign, the external roles in supporting him, and the situations of King Yūsuf dhū Nuwās on external roles in southern Arabia.