What was the approximate size of the Persian military forces?

The choice of approximately 150,000 troops is often cited based on historical accounts concerning the size of the Persian military forces, especially during significant campaigns such as the Greco-Persian Wars. This figure is derived from estimates made by ancient historians, notably Herodotus, who documented the Persian Empire's military engagements and provided estimates of troop numbers.

During these expansive campaigns, particularly the invasion of Greece, the Persian military showcased its vast size and diversity, drawing from various regions of the empire. This large force was a reflection of the technological and administrative capabilities of the Persian Empire, which enabled it to organize, equip, and mobilize a substantial number of troops effectively.

The estimates of military strength often fluctuate in historical texts, but 150,000 has become a commonly accepted figure for key battles, making it a reasonable approximation of the Persian military forces during this period.