The battle of Syracuse (or of the Anapus River) of 415 BC was an Athenian victory won close to the shore south of the city of Syracuse, but one that had no impact on the long-term outcome of the Sicilian expedition, which ended in total defeat (Great Peloponnesian War). The Athenian expedition to Sicily began rather badly. As their large fleet sailed around the Italian coast city after city refused to ally with them, or often even to allow them to buy supplies. Even their allies at Rhegium refused to get involved. The Athenians also discovered that the money they had been promised by Segesta, the city that had originally asked for their help, would not be forthcoming (and didn't actually exist). Faced with these early setbacks the three Athenian generals - Nicias, Alcibiades and Lamachus - each suggested a different plan. Nicias wanted to go directly to the aid of Segesta by attacking their enemy Selinus, then see if any Sicilian support was forthcoming. If not the fleet should return home. Alcibiades wanted to try and win allies everywhere in Sicily, and especially at Messenia, at the north-eastern corner of the island. They could then lead a major army against Syracuse from this strong base. Lamachus wanted to make a sudden attack on Syracuse, hoping to catch them unprepared and either win the war in one stroke or at least establish a siege of the city before it was fully stocked.
Alcibiades got his way, but at first his attempts to find allies met with failure. Messenia refused to let the Athenians in, as did Catane, half way between Messenia and Syracuse. The Athenians then sent ten ships into the Great Harbour of Syracuse to check the state of the defences, before returning to Catane, where this time they were admitted to the city, and finally gained a new ally on Sicily. Soon after this Alcibiades' career suffered a major setback. Back in Athens he had been accused of impiety, and the city's official trireme arrived to arrest him. He was forced to leave Sicily, although managed to escape arrest and took refuge in the Peloponnese.
This left Nicias and Lamachus in charge of the expedition, with Nicias as the senior partner. Although Athens had sent a large army to Sicily, it was weak in cavalry. In contrast Syracuse could field a large cavalry force, making it difficult for the Athenians to move on land. The Athenian generals realised that they needed to find a way to negate the Syracusan cavalry, and Nicias came up with an ingenious plan. An Athenian agent from Catana was sent to Syracuse, and informed the generals there that the Athens slept some way from their arms. If the Syracusan army marched on Catana, local supports in the city would make sure that the Athenians couldn't reach those weapons, allowing the Syracusans to win an easy victory. If the Syracusans took the bait and left their city, the entire Athenian army would be transported down the coast to Syracuse. Once there they would take up a strong position at the southern end of the Grand Harbour, where the Syracusan cavalry couldn't be used, and hopefully fight a battle on their own terms.
The plan worked exactly as hoped. The Syracusans fell for the story, and marched towards Catana. The Athenians and their local allies sailed south, and landed at the southern end of the harbour. They occupied a position between the coast and the temple of Zeus, protected by steep slopes on their left flank and the sea on the right. A fort was built behind their line to protect their rear.
The Syracusan cavalry discovered that something was wrong when they reached Catana and found that the entire Athenian fleet had put to sea. The army turned round and headed back to Syracuse, where they found the Athenians in a strong defensive position. After a brief face-off the two sides camped for the night, in preparation for a battle on the next day.
The Athenians formed up with their own troops in the centre, the Argives and Mantineans on their right (near the coast) and their other allies on the left. Only half of the army was placed in the front line. The other half formed a hollow square behind line, with orders to protect the baggage and reinforce any part of the line that looked to be in trouble. The Athenian hoplites were drawn up eight deep. Facing them the Syracusans were drawn up sixteen deep, suggesting that the two armies were about the same size. Their cavalry was posted on their right, but wasn't expected to play a major part in the battle.
The Athenians began the battle, advancing to attack. This caught the Syracusans by surprise, but they were able to resist the Athenian advance, and a hard-fought battle followed. This worried the Athenians, who had not expected such a hard fight, but eventually the Syracusan line began to give way. Their left wing, near the coast, was the first to suffer, and was pushed back by the Argives. The Athenians then broke the centre of the Syracusan line. With their line broken, the rest of the army began to flee. The Athenian inferiority in cavalry now prevented them from turning their victory into a rout. The Syracusan cavalry was able to protect their retreating troops, and the army rallied on the road to Helorus (this took them away from Syracuse, but the Athenians had cut the main bridge across the River Anapus, which ran between the city and the battlefield. The Syracusans suffered 260 dead, while the Athenians only lost 50 men, and appeared to be in a strong position to threaten the city.
In the aftermath of the battle the Syracusans were able to occupy the hill of the Temple of Zeus, close to the left flank of the Athenian army. Nicias was a superstitious commander, and may have avoided occupying this position for religious reasons, or perhaps to make sure that any plunder went to Athens and wasn't looted by the army. Whatever the reason, the Athenians would suffer for this mistake during the upcoming siege. Nicias then made a second mistake. Instead of moving to besiege the city while the inhabitants were still coming to terms with their defeat in battle, he decided to retire back to Catane for the winter and resume the siege in the following spring. This allowed the Syracusans to recover from their defeat. It also encouraged the Spartans to declare war on Athens in 414 BC, and with their help the Syracusans successfully resisted the Athenian siege, before in 413 BC the entire Athenian army was destroyed while attempting to retreat from the city.