The answer is Emperor Hulagu. He sent wanted the Caliph (Al-Musta'sim) to demanded him to surrender the Capital. He promised to continue a governance and security to the land. However, Caliph (Al-Musta'sim), did not agree to Hulagu's terms and demands. The Caliph (Al Musta'sim) refused despite the weak military condition of his territory. Hulago made an embargo on Baghdad and soon entered the city and killed Abbasi caliph (Al-Musta'sim ).