The Achaemenid Empire, also known as the first Persian Empire or Medo-Persian Empire was a major ancient civilization that was based in modern day Iran around 600 BC. The Achaemenid Empire is famous in the western world for having been the archetypal foe engaged against the Greek city-states in many famous ancient battles over territory and sovereignty known as the Greco-Persian Wars. It also later famously conquered by Alexander the Great.
The name Achaemenid comes from the name of a hypothetical king Achaemenes who ruled the Persis region from 705-675 BC. The Persian Empire was known to have been founded by a man named Cyrus II the Great who unified many of the tribes throughout the region in order to create a massive unified empire.
Eventually the Achaemenid Persian Empire would grow to own the territory previously occupied by the Median Empire as well as expand to encompass nearly all of Mesopotamia and even include Egypt. One major reason for the Achaemenid Empire's success lay in the sophisticated development of its roads and postal system for transport of trade goods and the military that also allowed messages to be carried successfully across great distances. Massive public works projects going back to the Akkadian Empire helped facilitate the movement of military units and communication in order to maintain the vast territories conquered.