Mahmud II became the Sultan of the Ottoman Empire and assumed the title of Caliph of Islam during a period fraught with challenges for the empire. Following the deposition of his brother Mustafa IV, Mahmud was proclaimed sultan after a quick succession of events that underscored the political instability within the empire. He faced several pressing issues, including military weaknesses, administrative corruption, and the pressing rise of nationalist movements among various ethnic groups within the empire, notably the Greeks and Serbs, who were pursuing independence. His early reign was characterized by a determination to consolidate his power and implement reforms that would rejuvenate the empire.

One of Mahmud II's most significant moves was to initiate extensive reforms in military and administrative sectors. He recognized that the traditional Janissary corps was outdated and often obstructed necessary reforms. In 1826, he famously dissolved the Janissaries in an event known as the "Auspicious Incident," which allowed him to build a modern army. Additionally, Mahmud undertook various civil reforms to modernize the bureaucratic structure and enhance the educational system, laying foundational changes that would lead to the Tanzimat reforms later in the century. His reign thus represented a crucial pivot point for the Ottoman Empire as it navigated the pressures of modernization in the face of increasing European dominion.

Moreover, Mahmud II's role as Caliph served to solidify his legitimacy not just as the political leader of the empire but also as a spiritual figure for Muslims under Ottoman rule. This dual authority was particularly vital as nationalist sentiments were on the rise, and various ethnic groups sought autonomy or independence from Ottoman rule. By positioning himself as Caliph, Mahmud aimed to maintain cohesion within the empire through Islamic unity while also reasserting the central authority of the sultan. His policies and reforms greatly influenced the 19th-century trajectory of the Ottoman Empire and set the stage for subsequent reform movements and conflicts.