Julian enters Constantinople as sole Roman Emperor.

Julian was the Caesar of the West from 355 to 360 and Roman emperor from 361 to 363, as well as a notable philosopher and author in Greek. His rejection of Christianity, and his promotion of Neoplatonic Hellenism and religious tolerance in its place, caused him to be remembered as Julian the Apostate in the Christian tradition.

Constantinople was a historical city located on the Bosporus that served as the capital of the Roman, Byzantine, Latin and Ottoman empires between its consecration in 330 and 1930, when it was renamed Istanbul. Initially as New Rome, Constantinople was founded in 324 during the reign of Constantine the Great on the site of the existing settlement of Byzantium and in 330 became the capital of the Roman Empire. Following the collapse of the Western Roman Empire in the late 5th century, Constantinople remained the capital of the Eastern Roman Empire, the Latin Empire (1204–1261) and the Ottoman Empire (1453–1922). Following the Turkish War of Independence, the Turkish capital moved to Ankara. Although the city had been known as Istanbul since 1453, it was officially renamed Istanbul on 28 March 1930. The city is today the largest city in Europe, straddling the Bosporus strait and lying in both Europe and Asia, and the financial center of Turkey.

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The term emperor is a modern convention, and did not exist as such during the Empire. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Another title used was imperator, originally a military honorific, and caesar, originally a cognomen. Early emperors also used the title princeps alongside other Republican titles, notably consul and pontifex maximus.