493 BC

In 493/492 BC, construction of fortifications in the Piraeus was begun on the advice of the Athenian statesman Themistocles. During the First Persian War, the Athenians defeated the Persians on land in 490 BC in the famous Battle at Marathon. After that battle, Athens felt safe from the Persian threat and saw no need for naval expansion. Themistocles, however, was convinced that the Persians would return with an even greater force. As proof he cited the Delphic Oracle, which foretold that Athens would be protected only by 'walls of wood'. Themistocles succeeded in persuading his fellow citizens to use the rich strike of silver at nearby Laurion to finance the construction of a large fleet of triremes, thus turning the city into a first-rate naval power.

480 BC

In 480 BC, ten years after the Athenian victory at Marathon, the Persian king Xerxes invaded northern Greece with an enormous army and a huge fleet. In this, the Second Persian War, the trireme served as the ship-of-the-line for both the Greek and Persian navies.

The first naval skirmishes between the Greek fleet and the much larger Persian fleet took place at Artemisium in the autumn of 480 BC but were not decisive. The Greek fleet fell back to the island of Salamis after the heroic last stand of the Spartan king Leonidas at Thermopylae. The Greeks were severely outnumbered both on land and at sea, but Themistocles managed to keep the Greek allied fleet and army together. Against all odds they defeated the Persian navy at Salamis. The victory secured Greek command of the sea, forcing Xerxes to retreat. The next year, in August of 479 BC, an allied force of Greeks decisively defeated the Persians in the Battle of Plataea.

478 BC

In 478/477 BC, in the aftermath of the Second Persian War, an alliance of Greek city-states formed the Delian League to take the fight to Persia. At the height of its power the League included nearly 400 member states, each contributing warships or money to the League's treasury on the sacred island of Delos.

The Delian League carried out several expeditions against the Persians in Thrace, Asia Minor and Egypt. In time the League, headed by Athens, controlled the majority of the Aegean Sea and the Hellespont.

In 454 BC, the League's treasury was moved from Delos to Athens after a failed expedition against the Persians in Egypt. In Athens, ten per cent of the annual tribute was given as a votive gift to Athena, the patron goddess of the city. This period is considered the Golden Age of Athens, for it witnessed the construction of several magnificent buildings, particularly the Parthenon, under the leadership of Pericles.

Allied tribute to the Delian League enabled the growth of Athens' naval empire throughout the fifth century BC. It also served as a source of contention between the preeminent powers of the Greek world, Athens and Sparta. Their rivalry broke out into open conflict during the long Peloponnesian War.

431 BC

In 462 BC, fighting broke out between members of the Delian League, led by Athens, and the Peloponnesian League, led by Sparta. A truce, the so-called Thirty Years' Peace, was initiated in 446 BC but lasted no longer than fifteen years.

Corcyra (modern Corfu), a colony of Corinth, was embroiled at this time in a conflict with its mother-city. Athens assisted Corcyra against Corinth, which was also an ally of Sparta. This led to the outbreak of the Peloponnesian War in 431 BC. The Athenian fleet, based in the Piraeus, dominated the naval engagements in the long struggle that followed.

Just as Athens relied on the Delian League, so Sparta found support in the member cities of the Peloponnesian League, which had superior troops on land. Soon Sparta had Athens under siege. Each spring between 431 and 421 BC, the Spartan army returned to Athens to burn down the fields around the city. The people of Athens and the surrounding countryside of Attica sought refuge behind the city walls, including the Long Walls, which connected the city to the port in the Piraeus. The siege of Athens left her inhabitants starved and menaced by plague.

In 415 BC, after an armistice lasting six years, the war spread to Sicily and southern Italy. In a failed expedition to Sicily, Athens lost a large portion of her fleet, giving Sparta the opportunity to strengthen her position in the war. Athens managed to rebuild and regain some semblance of her former supremacy at sea, but in 405 BC, in the Battle of Aegospotami, her dreams were crushed when the Spartans destroyed most of the Athenian fleet. In 404 BC, Sparta dictated the terms of peace and installed an oligarchy, the Thirty Tyrants, in Athens. Under their oppressive regime, most of the shipsheds in the Piraeus, as well as the famed Long Walls, were demolished as part of Athens' disarmament.

394 BC

In 394 BC, just ten years after the Peloponnesian War, Conon spearheaded the Athenian naval recovery with his success over a Spartan fleet at the Battle of Cnidus. Conon expanded and rebuilt major portions of the fortifications in the Piraeus. In 378 BC, a Second Delian League was founded. However, it never achieved the strength of its predecessor. With the rise of Macedonia under Philip II and Athens' defeat at the Battle of Chaeronea in 338 BC, the Second Delian League met its end.

322 BC

In June of 323 BC, after the death of Alexander the Great, Athens again made a bid for naval supremacy. The Athenian commander Euetion was defeated by the Macedonian commander Kleitos in two, possibly three, naval battles. The decisive battle was fought in 322 BC near the island of Amorgos in the southern Cyclades. The defeat shattered Athens' dreams of regaining her former status as one of the greatest naval powers of the Mediterranean.

86 BC

In 88 BC, Mithridates VI Eupator of Pontos challenged Roman power in the eastern Mediterranean. Athens sided with Mithridates, and in 87 BC Sulla arrived from Italy with a large army and laid siege to Athens and the Piraeus.

Although Mithridates reinforced the Piraeus from the sea, as the city had done in the fifth and fourth centuries BC, Sulla gained a victory without the aid of a fleet, and the Piraeus fell in 86 BC. The ensuing destruction left the Athenian shipsheds and the famous Arsenal of Philon in ruins.