Realizing how rich the Tahiride realm was, they decided to conquer it. The Mamluk army, with the support of forces loyal to Zaydi Imam Al-Mutawakkil Yahya Sharaf ad-Din, conquered the entire realm of the Tahiride but failed to capture Aden in 1517. The Mamluk victory was short-lived. The Ottoman Empire conquered Egypt, hanging the last Mamluk Sultan in Cairo. The Ottomans had not decided to conquer Yemen until 1538. The Zaydi highland tribes emerged as national heroes by offering stiff, vigorous resistance to the Turkish occupation. The Mamluks of Egypt tried to attach Yemen to Egypt and the Portuguese led by Afonso de Albuquerque, occupied the island of Socotra and made an unsuccessful attack on Aden in 1513.