They had a difficult relationship with the Mamluks of Egypt because the latter considered them a vassal state. Their competition centred over the Hejaz and the right to provide ''kiswa'' of the Ka'aba in Mecca. The dynasty became increasingly threatened by disgruntled family members over the problem of succession, combined by periodic tribal revolts, as they were locked in a war of attrition with the Zaydi imams in the northern highlands. During the last 12 years of Rasulid rule, the country was torn between several contenders for the kingdom. The weakening of the Rasulid provided an opportunity for the Banu Taher clan to take over and establish themselves as the new rulers of Yemen in 1454 CE.