ATTILA (406 – 453), Also known as Attila the Hun or the Scourge of God, was a the leader of the Huns from 434 until his death in 453 AD.  He was leader of the Hunnish Empire which stretched from Germany to the Ural River and from the Danube River to the Baltic Sea.  During his rule, he was one of the most fearsome and devastating of the Western and Eastern Roman Empire’s enemies.  He invaded the Balkans twice; he marched through Gaul (France) as far as Orleans before being defeated at the Battle of Chalons.  He refrained from attacking either Constantinople or Rome.
The origin of the Huns has been the subject of debate for centuries; however it can be said with general agreement that they may have been a confederation of Central Asian and European tribes, many of them nomadic horsemen.  Many experts believe them to be Turkic people descended from the Xiongnu tribes that menaced China as early as the 5th century BC.  The first emperor of China, Qin Shi Huangdi, built part of the Great Wall to keep the Xiongnu out.  In much of Western Europe, he is remembered as the epitome of cruelty and rapacity.  He played a major role in three Norse sagas.
The Huns, satisfied with a treaty with Theodosius, King of Byzantine Empire at the time, returned to their home in the Hungarian Great Plain, perhaps to consolidate and strengthen their empire.  Emperor Theodosius used this opportunity to strength the walls of Constantinople, building the city’s first sea wall and built up his border defenses along the Danube. After a few years of shared kingships, Attila became the sole ruler of the Huns.
The Huns remained out of Roman sight for the next few years as a Hunnish force invaded the Persian (Greek) Empire.  A defeat in Armenia by the Sassanid Persians caused them to abandon this attempt and return their attention to Europe.  Inn 440 AD, they reappeared in force on the borders of the Roman Empire.  They laid waste to Illyrian cities and forts on the river among them Viminacium, which was a city of the Moesians in Illyria. 
The Vandals under the leadership of Geiseric captured the Western Roman province of Africa with its capital of Carthage in 440 AD and the Sassanid Shah Yazdegerd II invaded Armenia in 441.  Theodosius had stripped the Balkan defenses of Roman Legions to help the defense of the Western Romans, now had to re-direct his attack to Africa to protect a main supply for food for Rome.  This created a clear path for Attila and Bleda through Illyria into the Balkans, which they invaded in 441. A lull followed in 442 allowing Theodosius to recall his troops from Sicily.  He financed a new operation against the Huns and thought it safe to refuse the Hunnish King’s demands.
Instead, Attila responded with a campaign in 443 AD.  Striking along the Danube, the Huns overran the military centers of Ratiara and successfully besieged Naissus (modern Nis) with battering rams and rolling siege towers – a military sophistication that was new to the Hun repertoire – then pushing along the Nisava they took Serdica (Sofia), Philippopolis (Plovdiv), and Arcadiopolis.  They encountered and destroyed the Roman army outside Constantinople and were stopped by the double walls of the Eastern capital.  A second army was defeated near Callipolis (modern Tallipoli) and Theodosius, now without any armed forces to respond, admitting defeat, sent the court official Anatolius to negotiate peace terms.  Attila died in 453 AD.
Their demands met for a time, the Hun kings withdrew into the interior of their empire.  According to Jordanes, sometime during the peace following the Huns’ withdrawal from Byzantium (around 445), Bleda died and Attiola took the throne for himself. 

The empire of Attila the Hun, circa 450 AD.