Yousef or Dhu Nuwas (the one with sidelocks) as known in Arabic literature, believed that Christians in Yemen were a fifth column. Christian sources portray Dhu Nuwas (Yousef Asar) as a Jewish zealot, while Islamic traditions say that he threw 20,000 Christians into pits filled with flaming oil. Dhu Nuwas left two inscriptions, neither of them making any reference to fiery pits. Byzantium had to act or lose all credibility as a protector of eastern Christianity. It is reported that Byzantium Emperor Justin I sent a letter to the Aksumite King Kaleb, pressuring him to “…attack the abominable Hebrew.” A tripartite military alliance of Byzantine, Aksumite, and Arab Christians successfully defeated Yousef around 525–527 CE and a client Christian king was installed on the Himyarite throne.
Esimiphaios was a local Christian lord, mentioned in an inscription celebrating the burning of an ancient Sabaean palace in Marib to build a church on its ruins. Three new churches were built in Najran alone. Many tribes did not recognize Esimiphaios’s authority. Esimiphaios was displaced in 531 by a warrior named Abraha, who refused to leave Yemen and declared himself an independent king of Himyar.
Emperor Justinian I sent an embassy to Yemen. He wanted the officially Christian Himyarites to use their influence on the tribes in inner Arabia to launch military operations against Persia. Justinian I bestowed the “dignity of king” upon the Arab sheikhs of Kindah and Ghassan in central and northern Arabia. From early on, Roman and Byzantine policy was to develop close links with the powers of the coast of the Red Sea. They were successful in converting Aksum and influencing their culture. The results concerning to Yemen were rather disappointing.
A Kendite prince called Yazid bin Kabshat rebelled against Abraha and his Arab Christian allies. A truce was reached once the Great Dam of Marib had suffered a breach. Abraha died around 570CE; Sources regarding his death are available from the qur’an and hadith. The Sasanid Empire annexed Aden around 570 CE. Under their rule, most of Yemen enjoyed great autonomy except for Aden and Sana’a. This era marked the collapse of ancient South Arabian civilization since the greater part of the country was under several independent clans until the arrival of Islam in 630 CE.
Advent of Islam and the three dynasties:
Muhammad sent his cousin Ali to Sana’a and its surroundings around 630 CE. At the time, Yemen was the most advanced region in Arabia. The Banu Hamdan confederation was among the first to accept Islam, second only to the Somalis, Afar and Habesha. Muhammad sent Muadh ibn Jabal, as well to Al-Janad, in present-day Taiz, and dispatched letters to various tribal leaders. The reason behind this was the division among the tribes and the absence of a strong central authority in Yemen during the days of the prophet.