The Bakil federation is the largest tribal federation in Yemen. Over 8 million men and women led by the Alshaif الشايف Family or clan Imam Yahya's campaign to subject the country, and more specifically the tribes, to his control, led him to undertake massive campaigns against their influence and power; in fact, his efforts succeeded in permanently eliminating all but two of the ancient confederations (the Hashid is the other one to survive). The member tribes of the Bakil Confederation are found primarily in the far north of the country; its leaders today are the ALSHAIF Family. The Known sheik is Naji Ben abdulaziz Alshaif. الشيخ ناحي بن عبدالعزيز بن عبدالله الشايف
Hashid and Bakil were the sons of Jashim bin Jubran bin Nawf bin Tuba'a bin Zayd bin Amro bin Hamdan. Bani Hamdan was already a well known clan in the 1st century AD and it was mentioned in Sabean inscriptions. Therefore, Hashid and Bakil (the brothers) must have lived in the BC era. In the Middle Sabaean period (the 1st to 4th centuries CE) the Bakil confederation consisted of three sha`bs - Raydah, Amran, and Shibam.
In the 3rd century most of Hamdan migrated to Syria. Hashid and Bakil switched their alliance to Himyar.
In the year 622, prophet Mohammed sent Khalid ibn Al-Walid to Yemen to call them to Islam. However, Khaled managed to push the Najrani and Tihami Yemenis into Islam but he didn't get a warm response from the Hamdani Yemenis of the highlands. So Prophet Mohammed sent over Ali bin Abi Talib and he was much more successful in converting the Hamdani Yemenis.
After the death of prophet Mohammed the Hamdan tribe remained Muslim and didn't join the ridda movement.
The Hamdan tribe remained on the side of Ali, after the defeat of Ali and later his sons. The tribes remained on alliance to Ali but didn't oppose the Umayyads or ally themselves with the other Shias.