Warmatrix

Artist impression of Huns crossing a river

The Huns were a nomadic people from the steppes of central Asia, who invaded Europe. In some ways they were the successors of the Scythians, though far more warlike.
The Huns came from somewhere in the central Asian steppes. Like many steppe peoples, they migrated westward, but did that so aggressively that they drove several other peoples before them into what is called the Great Migration, which spilled barbarians into the Roman empire. The Huns probably crossed the Volga river shortly after 370 CE and then accelerated their westward push. One by one they conquered or chased other steppe peoples: Sarmatians, Alans, Goths. The latter spilled into the eastern Roman empire, which sparked the Gothic War.
The Huns were not a single ethnic people, but more of a confederacy of warlike tribes. Many peoples that were conquered by them joined up with them. The Huns made their living from tribute and plunder and seemed to enjoy waging war. They did not always raid and conquer; as early as 380 CE they were employed as mercenaries by the Romans.
The Huns were horse nomads, herdsmen and hunters. On campaign they took cattle with them and relied on plentiful grassland for both cattle and horses. Most of their army was made up from horse archers and javelin throwers, nimble and fast. Their style of fighting was deliberately chaotic, to confuse their enemies and lure them into ambushes. At close quarters they employed spears, swords and also lassos and nets.
In 396 CE they reached the eastern Roman empire. They raided Thrace, Armenia, Cappadocia and even skirted Syria. During the 5th century CE they frequently fought and raided in Europe. They set up base in the Great Hungarian Plain, which offered plenty of grassland to feed their horses. This example would later by followed by other nomads like the Magyars and Mongols.
The Hun threat grew even more serious when in 434 CE the tribes were united under Attila and his brother Bleda, later under Attila alone. Under their leadership they alternated between exacting tribute from the Romans and raiding them. Only the Persian Sassanid empire was able to repulse the Huns, though also suffered some defeats. In the west the Huns suffered a temporary setback with their defeat at the Battle of the Cataulinian Plains, but this did not stop the raiding and plundering. The death of Attila 453 CE did. The Huns started fighting amongst themselves and within 16 years their empire collapsed. On the steppes they remained dominant into the 6th century CE, after which they were overtaken by the Turks.