Armies enter the Persian Empire
In 334 BCE, Alexander of Macedon crossed into Asia Minor and subsequently defeated Persian armies at Issus and elsewhere. Coastal campaigns included the siege of Tyre and entry into Egypt. Infantry, cavalry, siege specialists and supply transport worked together, drawing on local resources and negotiations. After Gaugamela, Babylon, Susa and Persepolis came under his authority, leaving Persian officials and regional elites to negotiate new political relationships.
Cooperation and conflict across distance
Campaigns into Iran, Bactria and the Indus region increased demands for routes, supplies and local cooperation. Alexander retained some officials, appointed Macedonians and founded or reorganized cities. Marriage, ceremonies and court practices became matters of government and disputes among soldiers. After fighting near the Indus, troops refused further eastward movement. The return involved difficult overland marches and coastal voyages, exposing the costs of sustained distant campaigning.
Rival generals and new kingdoms
Alexander died at Babylon in 323 BCE, and succession arrangements failed to stabilize his territories. Wars among commanders produced kingdoms ruled by dynasties including the Ptolemies and Seleucids. Greek-speaking residents lived alongside local institutions, religions and communities. Trade, soldiering and education encouraged movement, while courts sponsored buildings and scholarship. Agrarian revenues and provincial officers remained central to the cooperation and competition that organized these new states.