The war centered on mainland Greece, especially Attica, the Peloponnese, and central Greek regions, but extended across the Aegean. Athens relied on its port at Piraeus and maritime routes linking allied islands and coastal cities, while Spartan forces operated primarily from the Peloponnese. A major Athenian expedition carried the conflict to Syracuse in Sicily. Mountain barriers, sea passages, fortified cities, and access to grain supplies influenced campaigns throughout the eastern Mediterranean.