The End of the Roman Empire
After a brief period of peace known as the Pax Romana, which lasted about 200 years, Rome fell into a long slow period of decline. Instead of focusing on protecting their borders, Roman armies began fighting against one another. As a result, many outside invaders were able to enter Rome, and cause great destruction. These invaders included the Visigoths, the Huns, the Germans, the Persians, the Slavs, and the Avars.
By the late C.E. 400s Rome was completely overrun by these outside forces, and ceased to function as an empire. In C.E. 476 the German soldier Odoacer captured the city of Rome, and killed the emperor. He named himself king of Italy. Many historians consider this the official date of the fall of Rome.