How was the army organized in the Persian state?

The Persian Empire largely borrowed the experience of Assyria in creating its army, and significantly improved it. The Persian army also consisted of infantry, cavalry and navy. In the Persian army there was a special type of troops called immortals. In fact, they were the personal guard of the king. In addition, the Persian kings in their army could also use war elephants, however, their effectiveness was very doubtful, since an angry elephant in battle could cause more harm to his troops than to the enemy.