Attila and the Huns
The Huns were a nomadic people (not unsimilar to the later Mongols) who swept into Europe from central Asia around 370 AD and over the next 70 years built up a huge empire in Eastern Europe. They defeated the Goths in 376 in modern day Romania and this brought them in direct confrontation with the Roman Empire. Early Roman writers say they were nomads, had no settled home and knew nothing of agriculture. The huns loved to fight, plunder and pillage and as warriors they were unequaled at the time. They were amazingly accurate horse archers (again similar to the Mongols) and had complete command of horsemanship.
They learn't to ride as children and for the rest of their lives lived ate and slept either on or close to their horses. In battle they would make ferocious charges and unpredictable retreats and the speed of their strategical movements brought them victory after victory.
In 432 the Huns were united under two brothers Bleda and Attila. The joint rulers made a peace treaty with the Eastern Roman Empire who agreed to pay the Huns tribute in exchange for peace. The Romans never paid what was agreed and in 441 Attila launched an attack advancing almost to the Eastern Empire's capital of Constantinople.
In 445 Attila murdered his brother Bleda and launched a second devastating attack into the Eastern Roman Empire. The Romans sued for peace and bought off the Huns with Gold and Slaves.
In 451 Attila invaded the Western Empire's province of Gaul but was defeated by Roman and Goth forces at the great battle of the Catalaunian Plains. This was Attila's first and only ever defeat. In 452 Attila and his Huns were back when they invaded Italy herself and advanced on the city of Rome sacking Italian cities as they went. But famine and pestilence devastated the Hunnish armies near the gates of Rome and they were compelled to leave.
In 453 Attila planning a new invasion of the Eastern Roman Empire died on his wedding night, drunk from a nosebleed probably brought on by a stroke. He was around 50 years old.
In the aftermath of his death, his sons began to quarrel among themselves which ended in a brutal civil war between the brothers. This coupled with revolts from their subject peoples greatly weakened the Huns and their empire quickly began to collapse.
In 455 a combination of Goths, Gepidae and Heruli defeated the Huns in a great battle on the Nedao river in Pannonia. This defeat allowed the romans to secure their borders and the Huns faded from history.