The Dorian Syracusans might eventually come to the aid of the Dorian Peloponnesians.
The Syracusans were planning to invade Attica.
The Syracusans were scheming to take over all of Sicily.
The Peloponnesians were actively seeking an alliance with Syracuse.
He was unwilling to serve as the expedition's commander.
He didn't think it was possible for the Athenian forces to defeat the Syracusans.
He thought it was foolish to start another war when the peace with Sparta was still fragile.
He sought an expedition against the Spartans.
Blasphemy and plotting to overthrow Athenian democracy.
Homosexuality and plotting to set up a kingdom in Syracuse.
Pornography and improperly awarding military contracts.
Treason and plotting to betray Athens to the Spartans.
Their supplies were beginning to run out.
The allies they were counting on refused to join them.
They finally began to listen to Nicias's doubts.
They were frightened by the Syracusan fortifications.
The Athenian people.
Aristogiton and Harmodius
The lack of cavalry.
His forces were exhausted.
The defeated Syracusans retreated out of the range of his naval artillery.
The Syracusans fell back behind their walls.
Their democratic government.
Their war against Persia.
Their superiority of character.
He had decided the war against Syracuse would lead to an Athenian defeat.
He was summoned to Athens to face trial for plotting against the democracy.
He discovered a plot by Nicias to kill him.
He was a coward who couldn't face battle.
Penetration and pocket capture.
Buying off Syracuse's allies.
Circumvallation and blockade.
Building a large wooden badger and pretending to withdraw.