The decline of the Roman Empire refers to the gradual societal collapse

Societal collapse

Societal collapse broadly includes both quite abrupt societal failures typified by collapses , as well as more extended gradual declines of superpowers...

 of the Western Roman Empire

Western Roman Empire

The Western Roman Empire was the western half of the Roman Empire after its division by Diocletian in 285; the other half of the Roman Empire was the Eastern Roman Empire, commonly referred to today as the Byzantine Empire....

. Many theories of causality

Causality

Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....

 prevail, but most concern the disintegration of political, economic, military, and other social institutions, in tandem with foreign invasions and usurper

Usurper

Usurper is a derogatory term used to describe either an illegitimate or controversial claimant to the power; often, but not always in a monarchy, or a person who succeeds in establishing himself as a monarch without inheriting the throne, or any other person exercising authority unconstitutionally...

s from within the empire. The English historian Edward Gibbon

Edward Gibbon

Edward Gibbon was an English historian and Member of Parliament...

, author of The Decline and Fall of the Roman Empire (1776) made this concept part of the framework of the English language, but he was not the first to speculate on why and when the Empire collapsed.