By: Mir M.Hosseini
In the time of the Sassanid king Yazdgerd I, after two years of evaluation, the Iranian army was divided to four divisions as follows: First army stationed in was Marv to defend the country against the yellow coming from far east and China. This army was designated fixed and it was not to be used anywhere else. Border patrol units were installed and the army's cavalry to infantry ratio was 1:2. The second army was itself divided into two divisions stationed at East and West sides of the Caspian sea in order to prevent attacks from Khazars and the army's cavalry to infantry ratio was 1:4. The third army stationed at Tisfun was to protect the West and North of the country and the capital. It's main goal was to resist until support from the second or fourth army arrived. The fourth army was stationed in Sepahan. Except for defending Sistan and Kandahar, it's goals were more training and recruiting new forces. This military organization was kept until the end of the Sassanid dynasty.