Darius conquered large portions of Eastern Europe, even crossing the Danube to wage war on the Scythians.

[10] Darius ordered a halt at the banks of Oarus, where he built "eight great forts, some eight miles distant from each other", no doubt as a frontier defence.

After chasing the Scythians for a month, Darius's army was suffering losses due to fatigue, privation and sickness.

[11] Concerned about losing more of his troops, Darius halted the march at the banks of the Volga River and headed towards Thrace.

[10] In strategic terms, Darius must have seen that some Scythian-type peoples extended from Ukraine all the way to what is modern-day Uzbekistan, forming a continuum of dangerous nomadic raiders.

[10] Though Herodotus does not mention the season of the year, as Fol and Hammond write, it is possible to infer it, knowing that if Darius marched from Susa in spring 513 BC, he would have reached Chalcedon in May, and mustered his forces on the European side in June.

[1] He failed to bring the Scythians to battle, he was unable to secure any territorial gains and he did not even complete the building of the forts at what could have been a frontier.

[16] Allied groups to the Scythians included the Tauri, Agathyrsi, Neuri, Androphagi, Melanchlaeni, Budini & Gelonians, Sauromatae, and Getae.

Herodotus was correct in his assessment that the Scythians owed their escape to their mobility, their lack of inhabited centres, and the skill of their mounted archers.

He furthermore states that their refusal to submit to Persia was due to such factors as the authoritarian power of the kings, the widespread hatred of foreigners (IV.76.1), and the ordinary man's belief that what brought him and his tribe honour was the killing of enemies.