Ottoman Empire — Hakan

His conquest of Constantinople in 1453 prompted Mehmed to style himself as heir to both the Roman Caesars and the Turkic Qaghans; his full title included 'Khan of Khans, Sultan of Sultans'; as a descendant of the Mongolian Genghisid tradition through the Germiyanid and Anatolian beylik heritage, his claim to the Hakan title had both cultural and genealogical dimensions; Ottoman imperial documents from his reign use Hakan as a standard element of the sultanic titulature

Maintained the Hakan title as a standard component of Ottoman ceremonial style; his reign saw the Ottoman state consolidate its institutional use of the full titulature, including Hakan, in diplomatic correspondence with both Islamic and European powers

Added the Caliphate to the Ottoman titulature after his defeat of the Mamluk Sultanate and entry into Cairo in 1517; his full title thereafter combined Sultan, Caliph, and Hakan — representing the three great streams of Islamic, Arab, and Turkic-steppe legitimacy in a single ruler; Safavid Persian court poetry addressing Selim uses Khaqan as a primary honorific

Used the formulation 'Khagan of the Two Seas' — reflecting dominion over the Mediterranean and Black Sea — as a distinctive element of his imperial titulature; his chancellor Ibrahim Pasha composed elaborate titulature documents for the Habsburg and Safavid courts that place Hakan prominently; Suleiman's reign represents the apex of Ottoman claims to universal sovereignty drawing on both Islamic and Turkic-steppe legitimacy traditions

His reign saw the continued use of Hakan in standard Ottoman diplomatic correspondence; the title featured in the official Ottoman formula used in capitulations (treaties) granted to European trading powers

Conducted extensive correspondence with the Uzbek Shaybanid rulers of Transoxiana using the Hakan title as a mark of shared Turkic-steppe heritage; his outreach to the Central Asian steppe tradition was partly motivated by the shared Sunni–steppe identity against Safavid Shia Persia

Maintained the Hakan title in standard Ottoman ceremonial use; his reign coincided with the Long Turkish War against the Habsburgs, in which Ottoman diplomatic documents circulated widely in Europe and gave European chancelleries extensive exposure to the full Ottoman titulature including Hakan

Commissioned the Blue Mosque (Sultan Ahmed Mosque) in Constantinople; imperial inscriptions and waqf documents from his reign include Hakan in the full sultanic titulature in the established Ottoman formula

His campaign against Safavid Persia and the recapture of Baghdad in 1638 prompted extensive use of the Hakan title in victory proclamations; Safavid Persian sources responding to Murad's campaigns use Khaqan as his primary honorific, reflecting its recognition across the Islamic world

The Great Siege of Vienna in 1683 under his reign was the last major Ottoman military thrust into Europe; campaign documents and correspondence use the full titulature including Hakan; the defeat at Vienna and subsequent Treaty of Karlowitz (1699) marked the beginning of Ottoman territorial contraction

Conducted major modernizing reforms (Tanzimat precursors) including abolition of the Janissary Corps in 1826; despite sweeping reforms to Ottoman institutions, the traditional sultanic titulature including Hakan was retained in official documents throughout his reign, reflecting the title's deep ceremonial embeddedness

Emphasized pan-Islamic legitimacy through his Caliphate claims more than Turkic-steppe heritage; nevertheless Hakan remained a standard element of the formal titulature in imperial firmans; his outreach to Muslim subjects across Central Asia and India drew on the combined Caliph–Hakan identity

Last Ottoman Sultan; the abolition of the Sultanate by the Grand National Assembly on November 1, 1922 ended the Ottoman use of the Hakan title; Mehmed VI's full ceremonial titulature, used in official documents until the final weeks of the Sultanate, preserved the unbroken Ottoman claim to the Turkic-steppe imperial tradition that had passed through the Göktürks, Seljuks, and Mongols