After the Roman Empire fell in 476 AD due to many reasons (Barbaric invasions, unstable government, over expansion, etc), there was a time of great despair called the Middle Ages. The Dark Ages, or the early Middle Ages, lasted from 476 AD to about 800 AD. They are called the Middle Ages because it took place between ancient and modern times. The Dark Ages was a time when various groups from the north and east moved into the former Roman lands. These groups soon evolved into states and a powerful ruler called himself a king. Throughout the Dark Ages, battles between states broke out. It was a time of confusion and chaos.
An image of a battle in the Dark Ages