Roman emperor
The Western Roman Empire collapsed in the late 5th century. Romulus Augustulus is often considered to be the last emperor of the West after his forced abdication in 476, although Julius Nepos maintained a claim recognized by the Eastern Empire to the title until his death in 480. Following Nepos' death, the Eastern Emperor Zeno abolished the division of the position and proclaimed himself as the sole Emperor of a reunited Roman Empire. The Eastern imperial lineage continued to rule from Constantinople ("New Rome"); they continued to style themselves as Emperor of the Romans (later βασιλεύς Ῥωμαίων in Greek), but are often referred to in modern scholarship as Byzantine emperors. Constantine XI Palaiologos was the last Roman emperor in Constantinople, dying in the Fall of Constantinople to the Ottomans in 1453.
Theodosius I
Theodosius I (; ; 11 January 347 – 17 January 395), also known as Theodosius the Great, was a Roman Emperor from 379 to 395, and the last emperor to rule over both the Eastern and the Western halves of the Roman Empire. On accepting his elevation, he campaigned against Goths and other barbarians who had invaded the Empire. His resources were not sufficient to destroy them or drive them out, which had been Roman policy for centuries in dealing with invaders. By treaty, which followed his indecisive victory at the end of the Gothic War, they were established as "foederati", autonomous allies of the Empire, south of the Danube, in Illyricum, within the Empire's borders. They were given lands and allowed to remain under their own leaders, a grave departure from Roman hegemonic ways. This turn away from traditional policies was accommodationist and had grave consequences for the Western Empire from the beginning of the century, as the Romans found themselves with the impossible task of defending the borders and deal with unruly federates within. Justinian I (527-565), intent upon recovering lost regions, reversed the policy with the conquest of North Africa and Italy. Theodosius I was obliged to fight two destructive civil wars, successively defeating the usurpers Magnus Maximus in 387-388 and Eugenius 394, not without material cost to the power of the Empire.