Immediately after the expedition to Sumatra, the Ottoman Empire suffered a major rebellion from one of their most important settlements. An uprising led by Zaydi Imam in Yemen created a lot of uncertainty in the region which Sokollu had to give imminent priority before taking any further action in Aceh. While the insurrection in Yemen started in the summer of 1567, it was not taking seriously by the Ottoman regime until later in the year, when most of the major cities in the region came under fire by the rebellious factions. It is believed that the cause of the dissatisfaction in Yemen was the intensified Ottoman involvement in the region as a prelude for an expansion in the Indian Ocean. The unhappiness in the Ottoman Yemen also went back to the rule of Governor Mahmud Pasha, a compatriot of Sokollu, who managed to produce large economic gains in the region at the expense of the wellbeing of the population. After Mahmud's wrongdoings in Yemen had been revealed, Sokollu decided to appoint Koja Sinan, who was assigned the responsibilities to appease the turmoils in Yemen.