Huns reached the Roman Empire
The Huns came on the European historical scene in 370 AD, during the late 4th century AD.
At first, the Huns crossed the Volga and conquered Alans, which was another civilization of nomadic, warring horsemen. Two years later, after that, the Huns attacked the Ostrogoths; they were Germanic Goths. Ostrogoths were frequently attacking the territories of the Roman Empire. Allans, Goths, and some of the Visigoths were conscripted into the Hunnic infantry. The Huns seemed unstoppable as they dominated the Goths and Visigoth lands, and they earned a reputation as the barbarians. By 395 AD, the Huns reached the Roman empire; some of the Romans believed that they were devils arrived from hell. Romans viewed Huns as the barbarians, and Attila's name was related to destruction, slaughter, and chaos. In 441 AD, when the Romans sent an army to Sicily and North Africa to battle Vandals, Attila took advantage of the situation and made a series of attacks into the Eastern Roman Empire. The Huns quickly stuck without warning and took the town of Constantia.
Invasion of Gaul and the Catalaunian battle
Attila's one of the most significant campaigns was an invasion of Gaul in 451. When Atila had already entered Gaul, Aerius, which was the leader of the West, reached the agreement with the Visigoth king, Teodoric, to combine their forces in confronting the Huns. However, Attila had almost occupied the Aurelianum before the allies arrived.The final engagement was a battle of the Catalaunian Plains. According to some historians and explorers, after furious fighting, the Visigothic king was killed, Attila withdrew and left the Gaul. That was the first defeat of Attila the Hun. After hours of dreadful battles, thousands of soldiers were killed, and this battle is considered as Attila's first military defeat. According to the legend, Attila the Hun consulted the sacrificed bones and saw the Southlands of his army would fall in the fight, before the battle. His warning came true the next day.