Roman Empire

The Roman Empire is conventionally dated from 27 BCE, when the Senate granted Octavian the title Augustus, ending the Roman Republic's civil wars and inaugurating the Principate. At its territorial peak under Trajan (117 CE), it stretched from Britain to Mesopotamia and encircled the Mediterranean, which Romans called Mare Nostrum ("Our Sea").

The empire is typically divided into phases: the Principate (27 BCE – 284 CE), in which emperors nominally shared power with the Senate; the Crisis of the Third Century (235–284 CE), marked by civil war, plague, and currency debasement; and the Dominate (from Diocletian's reforms in 284 CE), a more overtly autocratic system. Diocletian's tetrarchy and Constantine's founding of Constantinople in 330 CE shifted the empire's center eastward. After the death of Theodosius I in 395 CE, administration was permanently split between Western and Eastern courts.

The Western Roman Empire is conventionally said to have ended in 476 CE, when the Germanic leader Odoacer deposed the child emperor Romulus Augustulus. The Eastern Roman (Byzantine) Empire continued until the Ottoman capture of Constantinople in 1453.

For political researchers and MUN delegates, Rome's legacy is foundational:

• Roman law, codified in Justinian's Corpus Juris Civilis (529–534 CE), is the basis of most continental European civil-law systems.
• Concepts such as imperium, civitas, citizenship, the veto, and the senate inform modern constitutional vocabulary.
• Roman treaty practice, including foedera with client states, prefigures later notions of unequal treaties and protectorates.
• The empire's collapse is a recurring case study in scholarship on state failure, overextension, and migration pressures, notably in the work of Edward Gibbon (1776) and later historians like Peter Heather and Bryan Ward-Perkins.

The phrase Pax Romana (roughly 27 BCE – 180 CE) is still cited in debates over hegemonic stability theory.