Classical Age of the Ottoman Empire
Expansion continued during the first half of the reign of Suleiman I (r. 1520-1566), who conquered first Belgrade (1521) and Rhodes, before invading Hungary in 1526, defeating and killing King Louis II in the Battle of Mohács and briefly occupying Buda. Lacking a king, Hungary descended into civil war over the succession, and the Ottomans gave support to John Zápolya as a vassal prince. When their rivals the Habsburgs began to achieve the upper hand, Suleiman directly intervened by again conquering Buda and annexing it to the empire in 1541. Elsewhere, Suleiman led major campaigns against Safavid Iran, conquering Baghdad in 1534 and annexing Iraq. Ottoman rule was further extended with the incorporation of much of North Africa, the conquest of coastal Yemen in 1538, and the subsequent annexation of the interior.
Ottoman Empire
By the end of Suleiman's reign, the Empire spanned approximately , extending over three continents. In addition, the Empire became a dominant naval force, controlling much of the Mediterranean Sea. By this time, the Ottoman Empire was a major part of the European political sphere. The Ottomans became involved in multi-continental religious wars when Spain and Portugal were united under the Iberian Union, the Ottomans as holders of the Caliph title, meaning leader of all Muslims worldwide, and Iberians, as leaders of the Christian crusaders, were locked in a worldwide conflict, with zones of operations in the Mediterranean sea and Indian Ocean where Iberians circumnavigated Africa to reach India, and in the way, wage wars upon the Ottomans and it's local Muslim allies and likewise the Iberians passed through newly Christianised Latin-America and had sent expeditions that traversed the Pacific in order to the Christianize formerly Muslim Philippines and use it as a base to further attack the Muslims in the far east. In which case, the Ottomans sent armies to aid its easternmost vassal and territory, the Sultanate of Aceh in Southeast Asia. During 1600s the worldwide conflict between the Ottoman Caliphate and Iberian Union was a stalement since both powers where at similar population, technology and economic levels. Nevertheless, the success of the Ottoman political and military establishment was compared to the Roman Empire, by the likes of Italian scholar Francesco Sansovino and the French political philosopher Jean Bodin.