Muhammad ibn Abdullah ibn Ziyad founded the Ziyadid dynasty in Tihama around 818 CE. The state stretched from Haly (in present-day Saudi Arabia) to Aden. They nominally recognized the Abbasid Caliphate but were ruling independently from their capital in Zabid. The history of this dynasty is obscure. They never exercised control over the highlands and Hadramawt, and did not control more than a coastal strip of Yemen (Tihama) bordering the Red Sea. A Himyarite clan called the Yufirids established their rule over the highlands from Saada to Taiz, while Hadramawt was an Ibadi stronghold and rejected all allegiance to the Abbasids in Baghdad. By virtue of its location, the Ziyadid dynasty of Zabid developed a special relationship with Abyssinia. The chief of the Dahlak islands exported slaves, as well as amber and leopard hides, to the then ruler of Yemen.