The greatest of the Ottoman Sultan, a titan of law, culture, and war, Suleiman's reign saw the conquest of Persia and European territory, while at the same time laws were reformed and culture went through a period of exceptional flourishing and monumental building. A competent ruler who surrounded himself with advisors and counsellors of superior skill, his reign was widely praised as the Golden Age of the Ottoman Empire.
He was the only son of his father, Selim I (himself an exceptionally energetic, conquering Sultan), and ascended to the throne in 1520, and immediately began a campaign against the kingdoms of Europe. He conquered Belgrade and the mighty crusader fortress of Rhodes, but the most consequential of his victories was likely the Battle of Mohacs, at which Suleiman's janissaries and artillery destroyed the Hungarians, plunging that nation into a long period of decline. During the course of his campaigns in the west, he was able to lay siege to Vienna, but could not conquer it. Central Europe became a long-simmering conflict zone under threat from the Ottomans from the Balkans to Poland.
Three campaigns over twenty years against the Safavid Persians resulted in the Ottomans taking possession of most of Mesopotamia, including the rich prize of Baghdad. Ottoman naval forces, led by competent admirals, were able to control the entirety of the Eastern Mediterranean (although the Knights of St. John were able to hold onto Malta) and the Barbary corsairs were able to wreak considerable damage along the south coast of Europe.
Suleiman was surrounded by a cadre of excellent advisors, most famous of which was his Grand Vizier, Pasha Ibrahim, who had been raised as Suleiman's slave from their youth, and who came to become the most important man in the empire after the sultan. His wife, Roxelana, was another canny advisor who served as a diplomat and a manager of intrigue at Topkapi Palace. The architect and builder Mimar Sinan oversaw the construction of the majestic Selimye and Suleiman mosques (as well as hundreds of other monumental buildings), and Istanbul acquired much of its new, Islamic architectural style, merging with the old Byzantine styles. There were countless other lesser viziers, military officers, admirals, and academics whose competent contributions greatly enriched Suleiman's kingdom.
His epithet “the Lawgiver” refers to his efforts to reform the administration of the state. In this, he codified secular Ottoman law to run parallel to existing Islamic systems of jurisprudence, working with the Hanafi scholar Ebusuud Efendi. The happy result of their efforts was an Ottoman Empire which was, in comparison to some Christian states of the region, a relatively tolerant, religiously pluralistic state. There are accounts of serfs and Jews fleeing the kingdoms of Europe to come and live under the relatively benevolent Ottomans.
Craftsmen and artists received special recognition of the state. Suleiman himself wrote poetry in Persian under a pseudonym (much of it is very good). He constructed schools to teach both religion and philosophy. Religious buildings and shrines throughout his empire received special attention, including the Dome of the Rock in Jerusalem and the Kaaba in Mecca.
During Suleiman's lifetime, the Ottomans were able to secure a series of alliances with European powers (most notably France) due to their ability to influence the course of affairs in Central Europe. A great deal of the political actions of the states of Europe during his lifetime can be seen as in response to the growing power, prestige, and wealth of the Ottoman Empire.
The end of Suleiman's reign was troubled. Pasha Ibrahim, his trusted advisor, was executed for conspiracy. Suleiman's succession was particularly fraught. Suleiman's son Mustafa was executed for attempting to seize power, and his other sons Selim and Bayezid began a succession war before their father died (Bayezid lost, and was executed). Suleiman himself died on campaign in Hungary.
The Ottoman Empire never again ascended to the heights he brought it. Future sultans would focus on the intrigue of their courts, leaving the administration of their empire to advisors and beys who would work at cross-purposes. No other sultan was capable of uniting powerful subordinates in a common cause, nor would they achieve military conquests on his scale. He was a rare kind of leader—one who achieves greatness in multiple domains, and encourages his subordinates to excellence in their own discipline.