Various economic and military policies instituted by Andronikos II, such as the reduction of military forces, weakened the empire and left it vulnerable to attack. In the mid-14th-century, the Ottoman Turks began a strategy of gradually taking smaller towns and cities, cutting off Constantinople's supply routes and strangling it slowly. On 29 May 1453, after an eight-week siege (during which the last Roman emperor, Constantine XI, was killed), Sultan Mehmed II "the Conqueror" captured Constantinople and declared it the new capital of the Ottoman Empire. Hours later, the sultan rode to the Hagia Sophia and summoned an imam to proclaim the Islamic creed, converting the grand cathedral into an imperial mosque due to the city's refusal to surrender peacefully. Mehmed declared himself as the new "Kayser-i Rûm" (the Ottoman Turkish equivalent of the Caesar of Rome) and the Ottoman state was reorganized into an empire.