Institutional evolution
Throughout the 14th and 15th centuries, therefore, the Ottoman state gradually reshaped its government and military institutions to meet the needs of administering and defending an expanding empire. This process naturally was influenced by those states that had preceded the Ottoman Empire, not only in the areas it came to rule but also in the lands of its ancestors. So it was that the developing Ottoman state was influenced by the traditions of the nomadic Turkic empires of Central Asia, particularly in military organization and tactics. It was also heavily influenced by the classical high Islāmic civilization of the ʿAbbāsids, as passed through the hands of the Seljuqs, particularly in the development of orthodox Islām as the basis of its administrative, religious, legal, and educational institutions and in the organization of its financial systems. In the court hierarchy, the central financial structure, and the tax and administrative organizations developed in the European provinces, the Ottomans were influenced by the Byzantines and, to a lesser extent, by the Serbian and Bulgarian empires. Although conversion to Islām was not demanded of the conquered, many Christians and a few Jews voluntarily converted to secure full status in the new empire. Most, however, continued to practice their old religions without restriction.
A particularly important source of Christian influence during the 14th century came from the close marriage ties between the Ottoman and Christian courts. Orhan was married to the Byzantine princess Nilüfer, mother of Murad I. Murad married Byzantine and Bulgarian princesses, and Bayezid I married Despina, daughter of the Serbian prince Lazar. Each of these marriages brought Christian followers and advisers into the Ottoman court, and it was under their influence that Bayezid I abandoned the simple nomadic courts and practices of his predecessors and isolated himself behind elaborate court hierarchies and ceremonies borrowed primarily from the Byzantines, setting a pattern that was continued by his successors. The triumph of Sultan Mehmed I in 1413 was due at least in part to the support of the Turkish notables and Muslim religious orders of Anatolia, who strongly resented the Christian predominance in Bayezid’s court and attributed his abandonment of the ghazi tradition and attacks in Turkish Muslim Anatolia—as well as the defeat at the hands of Timur—to Christian influence. As a result Turkish and Muslim influences dominated the Ottoman court during the 15th century, although the hierarchies, institutions, and ceremonies introduced in the previous century remained largely unchanged. The same process that isolated the sultans from their subjects also removed them from the daily administration of government. Formal institutions of administration therefore evolved to take their place, with the rulers delegating more and more of their duties to executive ministers, to whom the Seljuq title vezir (vizier) was given.
The continued close connections of the Ottoman family with the urban guilds and orders of Anatolia, many of the members of which were descendants of officials of the Great Seljuq and Il-Khanid empires, as well as the empire of the Seljuqs of Konya, provided continuity with the Islāmic Turkish traditions of government. With them came the basic unit of Islāmic administrative and financial organization, the mukâṭaʾa, which associated each office with a source of revenues and made each official the collector of his own salary. At the same time it circumscribed his administrative powers to those tasks directly involved with the financial function. It was relatively simple for the Ottomans to preserve previous methods of local taxation in different parts of the empire while weaving them into a united whole through the veneer provided by the mukâṭaʿa financial units, whose tax revenues were assigned to Ottoman officials. As the central administration was divided into functional departments, a vizier was appointed to direct each. Most of the early viziers were former Turkmen princes who had entered Ottoman service, though some, particularly under Bayezid I, were Christians and Christian converts. State policy was discussed and decided in a council (divan) of these viziers, who were joined by religious, judicial, and military leaders under the direction and chairmanship of the sultan. As the duties of the state became more extensive and complex, the individual viziers gained increased financial and political power, and, as the Byzantine influence caused the sultan to isolate himself, it was inevitable that the viziers would come to dominate the administration. As if to emphasize his removal from the daily affairs of state, the sultan began to appoint one of his viziers as his chief minister, or grand vizier (sadr-ı azem). From 1360 until the conquest of Constantinople, this powerful position was reserved for members of the Candarlı family, which came to lead and represent the powerful and assertive Turkmen notable families; these families thus benefited most from the 14th-century expansion of the empire.