Frederick II, Holy Roman Emperor, made a significant mark on the medieval politics of the Crusader states when he declared himself King of Jerusalem. This declaration followed a series of negotiations with al-Kamil, the Ayyubid Sultan of Egypt, during the Sixth Crusade, which was largely characterized by military campaigns aimed at reclaiming the Holy Land. Unlike many of his predecessors, Frederick II chose to pursue a diplomatic approach rather than outright warfare, culminating in the Treaty of Jaffa in 1229. This accord allowed for the peaceful transfer of Jerusalem to Christian control under Frederick's rule for a period of ten years.

The symbolic crowning occurred in the Church of the Holy Sepulchre in Jerusalem, which held immense religious significance for Christians worldwide. Frederick's ascension to the title of King of Jerusalem was not only a demonstration of his desire to unite Christendom but also an assertion of his legitimacy and power within the region. While his reign was met with mixed reactions from various factions, the event marked a notable shift in the dynamics of control and governance in the Holy Land, as it was executed without the bloodshed that characterized many previous Crusades.

However, Frederick's rule over Jerusalem faced substantial challenges, including skepticism from the Crusader states and opposition from the Papacy, which viewed his actions with caution. The tension was further complicated by Frederick's ambitions in the Mediterranean, especially concerning his competition with other Christian and Muslim leaders. Nevertheless, his crowning remains a pivotal moment in the history of the Crusades, showcasing how diplomacy could sometimes yield results that military might could not.