The purpose of this study is to examine a wide range of economic and military factors from the Third-Century Crisis to the fall of the Western Empire. This investigation of the Roman Economy focuses on taxation, inflation, coinage, mining, slavery and coloni. The section on the Roman Army addresses policy decisions of emperors, logistics, pay and supply of the armies, military losses and recruitment, strategies and tactics, and the overall decline in population across the empire. By taking this broad approach and examining numerous factors, this work will present a more complete explanation for the decline and eventual collapse of the Western Roman Empire.