So far, the most enduring Turkish state has been the Ottoman Empire that, within two centuries, developed itself from a small Turkish state (beylik) in Western Anatolia to a universal empire, stretching from the Adriatic in the West to the Red Sea in the East. Historians of differing backgrounds as well as orientations have been trying to grasp the factors initiating this rapid growth; a great variety of opinions have been put forward attempting to explain how this obscure perid of the Ottoman Empire was shaped. Paradoxically, while the success of Ottoman expansion was related to the Turkish-Islamic gazâ (holy war) ideology of Turcoman frontier forces, economic factors and social dynamics of the places Ottomans conquered have been neglected. The role of fütuvvat, indeed, in the success of classical period Ottoman sultans is undeniable. However, as important as Ottoman gazis religious motivations and the quest for booty were the conquest policy of Ottoman sultans that was institutionalized upon two principles: istimâlet and müdârâ. According to the doyen of Ottoman studies, Halil İnalcık, while the former means to win sympathy and support of local people through protection and reconciliation, the latter aims at cooperation among and peaceful coexistence of peoples of differing origins and religions for common political and economic goals. As stated in Ottoman historical sources, both have played decisive roles in the Ottoman conquests and the rapid spread of Ottoman rule. Just before the appearance of the Ottomans on the Balkan scene, for instance, the Byzantine rulers and local feudal lords were in a state of discord, not only politically but also socially and it was the dependent peasents who were suffering the negative consequences of this struggle over land. Consequently, after facing the protection of the Ottomans and their abolishment of forced labor a considerable majority of peasents welcomed the Ottoman domination.
The second important factor behind the Ottomans rapid success was the establishment of an institutionalized and central state system. Starting from Osman Bey the first Ottoman sultans soon realized that the collapse of previous Turkish states stemmed from the division of power among various clan leaders, which, in the final analysis, resulted in succession wars. The attempt for centralization was accelerated during the reign of Bayezid I but finally completed by Mehmed II who destroyed or eliminated all the possible obstacles standing in his way, first and foremost the frontier beys. Combined with a central treasury and well-established bureaucracy, Orhan Bey and Murad Is establishment of a standing and professional army under the direct command of the sultan, which laid the foundation for the janissary army, enabled the Ottoman sultans to gradually become absolute rulers. Peace in the Ottoman realm soon led to the emergence of a flourishing economic life and such Ottoman cities as Bursa, Denizli and Antalya grew as international markets. The state institution set up by early Ottoman sultans was so deep-rooted and strong that inspite of the crushing defeat in the War of Ankara (1402) Ottoman political structure could not be destroyed.
With the conquest of Constantinople in 1453 the Ottoman state became the most glorious state in the world. Following the conquest, Mehmed II claimed to be the sultan al-barrayn wa hakan al-bahrayn (the ruler of the two continents and the two seas). While the Ottoman rulers were fighting for the cause of Islam in Europe, the influence and power of Ottomans increased in Asia and the Islamic world accordingly. Selim I, subjugating another Muslim state, the Mamluks, began to use the title of hadim-ül harameyn (servant of holy places). By the death of Selim I in September 1520, the Ottoman state had doubled its territory, ranging to Egypt. Mehmed II had been stopped before the gates of Belgrade and it was Süleyman I (the Magnificent) who would capture the city in 1521, leaving Europe in despair. Sultan Süleyman started to use the title hilâfet-i rûy-i zemîn (the Caliphate of the entire world). During the time of Süleyman I, the Ottoman state became a universal empire. Ottomans were not only controlling a vast area with differing peoples, cultures and religions, but also were playing an active and decisive role in European diplomacy as in the Ottoman support for the Protestants in Europe.
The seventeeth century was alarming. Two long wars both beginning towards the end of the sixteenth century and continuing intermittently throughout the seventeeth century created deep crises in the Ottoman Empire. Wars with the Safavids between 1578-1639 and with the Habsburgs between 1593-1606 had had destructive impacts on financial, military as well as the demographic structure of the empire. With decreasing revenues and the price revolution, the Ottoman financial system was no longer able to meet the economic burden of wars launched on two fronts. The Ottoman state had to impose additional taxes in order to increase revenues but this led to social unrest and popular revolts in Anatolia. With the rise of ayâns throughout the eighteenth century, the central authority of the state was gradually collapsing. The empire had reached its natural borders, and thus, lost the opportunity of further expansion. Instead, it started to lose territory. The aforementioned wars, particularly the war with the Habsburgs, revealed the vital need for the modernization of the army. According to contemporary reform advisors, the main reason for the decline was the corruption of Ottoman classical institutions. Yet, the Ottoman intellectuals were not aware of the true causes for the decline.
In the classical age, on the other hand, with the support of Ottoman sultans unique examples of Turkish culture and art were created. The Sahn-ı Semân Madrasah, for instance, set up by Mehmed II following the conquest of Constantinople, soon became a leading scientific institution of its time. Different cities of the Ottoman realm, first and foremost Constantinople/İstanbul, became centers for scientific activities. While sultans encouraged the gathering of scholars in İstanbul, with the Ottoman conquests in the Balkans Islamic scientific tradition spread to Europe. Such classical period intellectuals as Tursun Beğ (Tarih-i Ebul-Feth), İbn Kemâl, Ebussuud Efendi, Lütfi Pasha, Kınalızâde Ali Efendi (Ahlâk-ı Alâî), Gelibolulu Mustafa Âlî (Nüshatüs-Selâtîn) have to be specifically mentioned. They were followed in the seventeenth century by Koçi Beğ, Kâtip Çelebi (Düstûrul-Amel li-Islâhil-Halel) and Hezarfen Hüseyin Efendi (Telhîsul-Beyân) and by Defterdar Sarı Mehmed Pasha in the eighteenth century. In the sixteenth century Takiyüddin er-Raşid established the famous İstanbul Observatory, while Ali Kuşçu, Fethullah Şirvanî and Hacı Pasha gained fame for their contributions to natural sciences. One of the most important relics of classical age Ottoman civilization is its architectural works. No doubt, Sinan has set his seal on the sixteenth century Ottoman architecture. During the classical age in İstanbul, along the Bosphorus in particular, magnificent mosques were built whose silhouettes exalt still above the seven hills of İstanbul.