Nikopol (Bulgarian: Никопол [niˈkɔpoɫ]; historically Greek: Νικόπολις, Nikópolis, Latin: Nicopolis, Turkish: Niğbolu) is a town in northern Bulgaria, the administrative center of Nikopol Municipality, part of Pleven Province, on the right bank of the Danube river, 4 kilometres (2 miles) downstream from the Danube’s confluence with the Osam river.

These milites praeventores are the only unit of this type recorded in the Notitia Dignitatum, and was a special regiment for active defense, including surprise actions, of the border sector.

When the border and the Roman Empire in the Lower Danubian lands were strongly threatened by unceasing Hunnic raids in 447, the inhabitants of Ansamus showed unexpected high spirit and enviable military skills, by which they not only repelled an enemy siege, but demanded conditions from Attila himself, according to Priscus.

The inhabitants of the town made raids far from their fortifications when their scouts informed them that enemies were passing, laden with Roman booty.

After the fall of Tarnovo in 1393, the last Bulgarian Tsar Ivan Shishman defended what remained of the Empire from the fortress of Nikopol, where he was captured after the town was conquered by the Ottomans in 1395.

At the fortress of Nicopolis, the united armies of Christian Europe headed by Hungarian king Sigismund and various French knights were defeated by the Ottomans under Bayezid I and his Serbian vassal Stefan Lazarević.

Under Ottoman rule, Nikopol developed into an important military and administrative centre as a sanjak, with a strong fortress and a flourishing economic, spiritual and political life, until it went into decline during the 17th and 18th centuries.