The Four Horsemen

Rome's decline came from four overlapping forces that no emperor could fully control:

• Military overstretch — Borders ran roughly 10,000 miles, impossible to defend everywhere at once
• Economic collapse — Debased currency caused runaway inflation, and trade networks broke down
• Barbarian pressure — The Huns pushed Germanic tribes westward into Roman territory like a chain reaction
• Political instability — Between 235 and 476 CE, most emperors were assassinated or overthrown

Each problem made the others worse. Defending borders cost money. Raising money required stability. Stability required military success. Military success required money. It was a death spiral.