They were not really helpmates of the Persians. They repelled a late 6th Century BCE invasion by Persia led by Darius I, who barely escaped wit help from some of the Ionian Greek city-states within his empire.
The following invasions: Aryans, Persians, Greeks, Scythians, Huns, Arabs, Turks etc. The climate, which was far from preferable for agriculture and forming a permanent settlement.
The Scythians and Xiongnu were nomadic societies.
Indo-Scythians ended in 400.
Indo-Scythians was created in 200.
Babylonians and Scythians.
Ovid among the Scythians was created in 1859.
The Xiongnu and Scythians greatly influenced Central Asia.
The Xiongnu and Scythians greatly influenced Central Asia.
The Sumerians and the Scythians
Russia.
Nomadic.
Romans and Greeks.