"The Huns were a collection of tribes from the Eurasian steppe, with a fearsome reputation (the Great Wall of China was built to keep them at bay). Basing themselves in what is now Hungary, they took advantage of the decline of the Roman Empire during the 4th and 5th centuries to expand their territories, until, at its peak under Attila, their empire stretched from the River Danube to the Baltic Sea, encompassing large swathes of Germany, Austria and the Balkans."