The investigating the Transformations of the

Achaemenid Empire Army became the most powerful army during Darius kingdom from structure and military style point of view. It had some modifications by Xerxes the king and he conquested Greece following his father's policies in Greece and modifying the structure and military style including follower tribes. The author attempts to study the actions of Xerxes the king in reorganizing the forces, tribes, military style and the reasons of their inefficiency in historic battles with Greece using analytic- descriptive approach. The question considered in this paper is what modifications did the Achaemenid Army have? Multi-nationality army, have new military tools and instruments, navy force enhancement for continuing expansions are the hypothesis investigated in this research. The developments that Khasharianasha created in the Achaemenid Army not only had a significant effect on the military's military performance, but also on the strength of Xerxes and its successive successes and the suppression of the enemies.