Husayn is highly regarded by Shia Muslims for refusing to pledge allegiance to Yazid, the Umayyad caliph, because he considered the rule of the Umayyads unjust. The annual memorial for him and his children, family and his companions is the first month in the Islamic calendar, that is Muharram, and the day he was martyred is known as Ashura (the tenth day of Muharram, a day of mourning for Shi’i Muslims).