History of the Constitution of the Roman Republic
The history of the Constitution of the Roman Republic is a study of the ancient Roman Republic that traces the progression of Roman political development from the founding of the Roman Republic in 509 BC until the founding of the Roman Empire in 27 BC. The constitutional history of the Roman Republic can be divided into five phases. The first phase began with the revolution which overthrew the Roman Kingdom in 509 BC, and the final phase ended with the revolution which overthrew the Roman Republic, and thus created the Roman Empire, in 27 BC. Throughout the history of the republic, the constitutional evolution was driven by the struggle between the aristocracy and the ordinary citizens.
Historiography of the fall of the Western Roman Empire
The Roman Empire emerged from the Roman Republic when Julius Caesar and Augustus Caesar transformed it from a republic into a monarchy. Rome reached its zenith in the 2nd century, then fortunes slowly declined (with many revivals and restorations along the way). The reasons for the decline of the Empire are still debated today, and are likely multiple. Historians infer that the population appears to have diminished in many provinces—especially western Europe—from the diminishing size of fortifications built to protect the cities from barbarian incursions from the 3rd century on. Some historians even have suggested that parts of the periphery were no longer inhabited because these fortifications were restricted to the center of the city only. Tree rings suggest "distinct drying" beginning in 250.