They received word that the Peloponnesian fleet was not coming.
They lost a series of major battles on the plains outside the city.
The Athenians were close to completing their siege walls.
Their leader Hermocrates died in battle.
The arrival of the Peloponnesian fleet and construction of a counterwall left his forces besieged from the land side.
He was timorous and frightened of the reputation of the Spartan general Gylippus.
He was alarmed by reports that his former colleague Alcibiades had gone over to the Spartans.
The promised reinforcements from Athens had not arrived and he knew he lacked the manpower to take Syracuse.
To destroy the lands providing sustenance to the Athenian population.
To take the city of Athens by surprise.
To prevent their allies from getting restive.
To force the Athenians to fight a two-front war.
They waited until a moonless night to set sail.
25 Corinthian triremes kept the Athenian ships distracted.
They dug a very long tunnel from the Peloponnesus to Sicily.
They defeated the Athenians in a major sea battle at Naupactus.
The Athenians were forced to withdraw from the Great Harbor of Syracuse.
The allies could replace their lost ships more easily than the Athenians could replace their lost troops, stores, and equipment.
It was the first time the Athenians had been defeated in battle since they arrived in Sicily.
It convinced the Athenians that they could not win the war.
He knew that his position would only weaken with time.
He didn't have sufficient supplies to delay.
He was a foolish and impatient general.
He hoped to stop the Syracusan counterwall before it extended further.
He thought Syracuse was close to collapse.
He feared to return to Athens in defeat.
He was convinced that with the reinforcements, their forces were still superior to the allied Syracusan-Peloponnesian forces.
He wasn't concerned so long as Athens held command of the sea.
Demosthenes's failure at Epipolae.
The arrival of Gylippus.
The closure of the Great Harbor.
The auguries that caused Nicias to delay withdrawal.
It was so crowded that it was similar to a land battle fought at sea.
The Athenians lost a sea battle.
The battle took place at night.
No ships were sunk on either side.