1. The Roman Republic transitioned into an empire after years of civil war and unrest. Julius Caesar's assassination and the conflicts involving the Gracchus brothers demonstrated the republic's inability to solve problems peacefully. 2. Under the empire, Rome was able to experience over 200 years of peace and prosperity known as the Pax Romana through strong central rule. However, military overexpansion and economic issues eventually led to decline. 3. The Roman Empire split into western and eastern halves administered from Rome and Constantinople, respectively, though both continued to build upon Roman traditions of law, architecture, and engineering for centuries.