During that period, Yemen was the sole coffee producer in the world. The country established diplomatic relations with the Safavid dynasty of Persia, Ottomans of Hejaz, Mughal Empire in India, and Ethiopia, as well. Fasilides of Ethiopia sent three diplomatic missions to Yemen, but the relations did not develop into a political alliance, as Fasilides had hoped, due to the rise of powerful feudalists in his country. In the first half of the 18th century, the Europeans broke Yemen's monopoly on coffee by smuggling coffee trees and cultivating them in their own colonies in the East Indies, East Africa, the West Indies, and Latin America. The imamate did not follow a cohesive mechanism for succession, and family quarrels and tribal insubordination led to the political decline of the Qasimi dynasty in the 18th century. In 1728 or 1731, the chief representative of Lahej declared himself an independent sultan in defiance of the Qasimid dynasty and conquered Aden, thus establishing the Sultanate of Lahej. The rising power of the fervently Islamist Wahhabi movement on the Arabian Peninsula cost the Zaidi state its coastal possessions after 1803. The imam was able to regain them temporarily in 1818, but new intervention by the Ottoman viceroy of Egypt in 1833 again wrested the coast from the ruler in Sana'a. After 1835, the imamate changed hands with great frequency and some imams were assassinated. After 1849, the Zaidi polity descended into chaos that lasted for decades.