From the sixth to fourth centuries BCE, the Persian empire under the Teispid and Achaemenid dynasties ruled most of western Asia and neighbouring regions, from the Indus river to Egypt and the coasts of the Aegean Sea. Despite the sources’ disproportionate emphasis on the failures of military expeditions against the overseas Greeks, the Persians enjoyed a lengthy period of military success and overall stability due in part to their rulers’ skill in the formulation of strategy. In the initial conquests, Persia absorbed peer competitors such as Babylon and Egypt; most subsequent conflicts pitted the empire’s superior forces against localised rebellions. Persia’s control stretched to vital subject communities in frontier zones and they also projected influence over external allies and clients. Persian kings rarely campaigned in person after the early expansionist phase, but relied on an exemplary communication system to manage satraps and other delegates tasked with provincial and frontier operations. To carry out military objectives, they relied on networks of provincial recruitment, supported as necessary by elements of a standing army associated with the royal court. Persian military activities were augmented by diplomatic outreach, most notably in Persia’s Greek relations after the failed invasion of mainland Greece. Persia’s strategic capabilities remained formidable until they were caught off guard by the tactical superiority of Alexander’s Macedonian invaders.