The siege of Plataea in 429-427 was a Theban
victory that saw them capture Athen's only ally in Boiotia, although only after
a two-year long siege. The city of Plataea was located on the southern edge of
Boiotia, the area to the north-east of the Gulf of Corinth. It was the only
Boiotian city that was not a member of the Boiotian League (dominated by
Thebes), and was instead an ally of Athens. This was not an entirely popular
policy inside the city, and two years before the start of the siege these
disputes inside the city led to the incident that triggered the Great Peloponnesian War.
In the spring of 43, with the outbreak of war looming, the Thebans decided to
try and take control of Plataea. They had the support of one of the political
factions inside the city, led by Nauclides, and decided to try and take
advantage of this to take the city without a struggle.
Two forces were sent from Thebes towards Plataea. The first consisted of 300
men. They were to be let into the city at night and take immediate control. The
second, much larger force, would follow some way behind in order to avoid
detection, arrive later on the same day and secure Theban control of Plataea.
The first part of the plan worked perfectly. The advance party of 300 men were
let into the city and took up a position in the market place. At first the
Plataeans were so shocked by the sudden appearance of 300 armed men inside the
city that they agreed to the Theban demands, but when it became clear how small
the invading force actually was the people of Plataea, including women and
slaves, turned against the invaders.
In a vicious night fight 120 of the Thebans were killed or escaped from the
city, while 180 were taken prisoner. The larger Theban force didn't arrive
until the following morning. They then agreed to withdraw from the city in
return for the safe return of the prisoners, but as soon as the Theban army was
gone the Plataeans executed their prisoners. This incident ended the last
lingering hopes of peace between Athens and Sparta, and triggered the Great
Peloponnesian War (431-404).
In the first two years of the war the main Sparta effort were two invasions of
Attica, but in the third year of the war Sparta and her allies decided to
attack Plataea instead. The Plataeans were clearly expecting an attack, for by
the time the Spartans arrived the women and children had left the city and had
taken refuge at Athens. When the siege began the city was defended by 400
Plataeans and 80 Athenian volunteers, supported by 110 women who cooked for the
The Spartan army, under the command of King
outside Plataea while negotiations went on. Both sides tried to use the memory
of the Persian War, when Plataea had been the site of the decisive land battle,
with the Plataeans calling on the Spartans to honour an earlier oath to
guarantee Plataea's independence, while Archidamus called on the Plataeans to
either join the Boiotian league or to remain neutral.
The Plataeans replied that they would have to consult the Athenians, and that
they were worried that the Thebans would use the proposed neutrality in a
second attempt to seize the city. Archidamus then came up with a dramatic
counter-offer, suggesting that the people of Plataea evacuate their city and
let the Spartans occupy it for the duration of the war. They would then be
allowed to return once the war was over. Rather surprisingly the Plataean
assembly agreed to these terms, but only if Athens approved. The Plataean
envoys returned from Athens with a reassurance that Athens would never abandon
them, and a promise that they would provide as much help as possible. This
encouraged the Plataeans to turn down the Sparta terms, and the siege finally
Archidamus began by constructing a wooden palisade around the city. The
Spartans then began to build a mound leading up to the walls, with the
intention of mounting an assault. The defenders responded by increasing the
height of their own walls opposite the mound. They also dug a tunnel from
inside the city to a position under the mound and began to excavate material
from inside it, both delaying the construction of the mound and providing
themselves with material for their own fortifications. Finally they began work
on an inner wall, curving around the area that the mound was heading for so
that if the Spartans did manage to cross the outer walls they would be faced
with a new line of fortifications. The Spartans also used more conventional
siege engines against the city, but these were ineffective. After this effort
had been going on for some time the Spartans decided that they couldn't take
the city using their siege engines.
Their next step was to wait for a suitable wind and then drop burning bundles
into the city from the end of their mound. A large part of the city was
destroyed by fire, but the defences remained intact. After this failure the
Spartans decided to simply blockade the city. A wall of circumvallation was
built around Plataea, most of the besieging army was dismissed, and the
blockage began. The Spartan walls were fairly elaborate. Two walls were built
(one facing the besieged the city, the other facing outwards to guard against
any relief effort), sixteen feet apart. The garrison lived in huts built
between the walls. The walls were linked by regularly spaced towers (ten
battlements apart according to Thucydides), with gates in the centre of each
tower. By the winter of 428-427 supplies were beginning to run out within the
city. The defenders decided to try and break out. At first this was to be a
mass breakout, but half of the garrison then decided that it was too risky, and
only 220 men took part.
They used ladders to climb over the inner wall of circumvallation, captured two
of the towers, and managed to get across the outer wall before strong
reinforcements could arrive. When a mobile force of 300 Peloponnesians did
arrive it was too late. The Plataeans then moved up the road leading to Thebes,
deceiving the besiegers, who attempted to find them on the road to Athens.
Eventually 212 of the escapees managed to reach Athens. Their efforts were in
vain. The Athenians didn't send a relief force to Plataea, as this might have
involved them in the formal battle that they were trying to avoid.
By the summer of 427 the defenders were so weakened by starvation that they
were unable to resist a Spartan attack. At this point the Spartan commander
decided to try and negotiate the surrender of the city, on the grounds that
conquered places would probably be returned in any peace treaty, while places
that surrendered might not be. The Plataeans agreed to surrender and to face
the judgement of Sparta, in a fair trial.
Instead they were faced with a mock trial, before the Spartans, under pressure
from their Theban allies, executed all 200 Plataean and 25 Athenians who had
survived the siege. The women who had remained in the city to cook for the
garrison were sold into slavery. Plataea itself was demolished, and the
building materials used to build a large two-storey hotel and a temple to Hera.
The land was then leased out to Thebans. Just as the Spartan commander had
expected, Thebes was allowed to keep Plataea in the Peace of Nikias of 421.