The fourth time period is the Dark Ages. The Dark Ages started with the split of the Roman Empire in 395 CE and lasted to 1492, when Columbus discovered America. This period included, the Crusades, the Bubonic Plague and the Hundred Year War, all of which caused extreme amounts of deaths. It also included the end of the Tang Dynasty that left China in disunity. Most important of all was that feudalism was the major form of government during this time.