Constantine's ruthless rise to power as emperor of the new Roman Empire | Anthony Kaldellis

Constantine emerged as the sole Roman emperor in 324 AD through a series of civil wars following the non-hereditary system established by Diocletian. Although initially passed over by the system in favor of merit-based succession, Constantine's military competence and popularity with the armies allowed him to defeat numerous rivals, including fathers-in-law and brothers-in-law. As Constantine gradually moved eastward during these conflicts, he defeated his final rival Licinius in 324 and chose the strategic location of Byzantium on the Bosphorus as the site for his new capital, Constantinople (New Rome).

Constantinople's geographical significance was paramount to Constantine's vision. Located at the intersection of Europe and Asia on the Bosphorus, the city occupied a midpoint between the two major imperial frontiers—the Danube in the north and the Euphrates in the east. Unlike Rome, which was geographically distant from these military frontiers, Constantinople allowed emperors to respond effectively to threats across the empire. The city also functioned as a unifying point between the Black Sea and Mediterranean, and historically, the empire had repeatedly fractured at the Bosphorus with one emperor ruling Europe and another Asia. Constantinople ultimately served as a "clamp" that kept these regions unified by creating a new Senate composed of 2,500-3,000 elites from the Eastern Mediterranean who became invested in the city's success.

Despite his consequential achievements, Constantine was ruthless and murderous. He eliminated numerous family members and allies whose usefulness had expired, most notably executing his competent and popular son Crispus and his wife shortly after defeating Licinius. The sources offer no justification for these murders, and contemporary historians simply erased Crispus from their records after his execution. Kaldellis ranks Constantine first among Byzantine emperors not because of his personal character but because his decisions—founding Constantinople and converting the empire to Christianity—were world-historical in their significance. While other top emperors performed their roles competently and improved their subjects' lives, Constantine's impact transcended normal imperial achievement.