The Achaemenid Persian Army (c. 550–330 BC) was a massive, diverse imperial force known for its reliance on light infantry, skilled cavalry, and archery rather than heavy armor. Organized on a decimal system (units of 10, 100, 1,000, and 10,000), it featured a professional core—notably the 10,000 "Immortals"—supported by vast levies from conquered nations.
The book contain a detailed study analyzing the composition, equipment, and tactical employment of the army, including its varied contingents.