For centuries Rome had expanded under strong emperors and solid armies, as you saw in the golden age of
Topic 17. Then, from about
235 CE, the empire entered a long nightmare historians call the
Crisis of the Third Century. It lasted until roughly
284 CE. Armies fought each other more than foreign enemies. Emperors rose and fell within months. Trade broke down. Cities emptied. Frontiers cracked. This was not one single battle. It was fifty years of overlapping disasters that nearly ended the Roman world. Understanding the crisis helps explain why later emperors like Diocletian rebuilt government from scratch.