When faced by a stronger force, the nomads could simply retreat deep into the steppe and wait for the invaders to leave. With no cities and little wealth other than the herds they took with them, the nomads had nothing they could be forced to defend. An example of this is given by Herodotus's detailed account of the futile Persian campaigns against the Scythians. The Scythians, like most nomad empires, had permanent settlements of various sizes, representing various degrees of civilisation. The vast fortified settlement of Kamenka on the Dnieper River, settled since the end of the 5th century BC, became the centre of the Scythian kingdom ruled by Ateas, who lost his life in a battle against Philip II of Macedon in 339 BC.