The siege of Chalcedon in 408 was part of an
Athenian attempt to regain control of the Bosphorus and ensure the safety of
Athens's food supplies from the Black Sea Peloponnesian War.
Chalcedon, on the Asian shore, and Byzantium, on the European shore, had been
part of the Athenian Empire, but both cities rebelled after the Athenian defeat
at Syracuse. The Athenians managed to regain control over the Hellespont at the
battle of Cyzicusi in 410, but
had to wait another two years before they were in a position to move against
Chalcedon and Byzantium.
The Chalcedonians were expected an attack in 408, and took the precaution of
sending their movable wealth to apparent safety with their neighbours in
Bithynia. The city was defended by the Chalcedonians and by a Spartan force,
and the defence was commanded by the Spartan 'harmost' Hippocrates. A Persian
army under the satrap
Pharnabazus was also in the area. The Athenian force had three commanders -
Thrasyllus and Alcibiades, and contained
at least 5,000 men and 70 ships. Alcibiades was probably in overall command,
and it was he who led a force of cavalry and heavy infantry into Bithynia,
where he seized the Chalcedonian's property. After this expedition the
Athenians constructed lines of circumvallation around Chalcedon, blockading the
city in one direction and protecting against the Persians in the other.
Hippocrates and Pharnabazus decided to try and break the siege with
simultaneous attacks. Hippocrates emerged from the city, and offered battle.
The Athenians accepted, and Thrasylus led their heavy infantry in an attack on
the Chalcedonians and Spartans. The battle was undecided until Alcibiades
attacked with a mixed force of infantry and cavalry. Hippocrates was killed,
and his army broke and fled back into the city.
Pharnabazus, who had been unable to break through the Athenian siege lines,
retreated back to his camp. After this battle Alcibiades left the Athenian army
to raise more money. This left Theramenes in command, and he soon came to an
agreement with Pharnabazus. He agreed to pay Athens twenty talents, while
Chalcedon agreed to pay her normal tribute to Athens. He also granted the
Athenians a safe conduct so that their ambassadors could visit the Persian
emperor. In return the Athenians would stop all hostilities against Chalcedon.
On his return Alcibiades was forced to take the same oath, although he only
agreed to do so after Pharnabazus agreed to exchange oaths of good faith with
The Athenian embassy was a failure. The Spartans had already come to an
agreement with the Persian emperor, and the Athenian ambassadors were detailed
in Persian Asia Minor for three years before finally being released. In the
meantime the Athenian army in the Bosphorus moved on to attack Byzantium, which
was betrayed to them after a siege.