The battle of Drepanum was the only major naval defeat suffered by the Romans during the First Punic War (they did however repeatedly loose fleets in storms). The defeat appears to have largely been caused by the poor leadership of the senior consul for the year, Publius Claudius Pulcher. He had inherited command of the siege of Lilybaeum, then entering its second year, and bogged down after a dramatic first year.
The events of the previous year had inflicted serious losses amongst the Roman sailors, leaving it apparently unable to conduct offensive operations. Reinforcements had been raised, shipped across to eastern Sicily, and then marched to Lilybaeum. On their arrival Claudius decided to launch a surprise attack on the Carthaginian fleet at Drepanum.
Claudius wanted to surprise the Carthaginian fleet in harbour. Accordingly, he took up position at the rear of the fleet, presumably to encourage speed. This meant that he was unable to influence crucial events as the battle developed.
The Roman attack nearly succeeded in gaining surprise. However, the Carthaginian admiral, Adherbal, reacted quickly once the Roman fleet had been sighted. He ordered his fleet to dash out to flee as quickly as possible. His ships thus escaped harbour, but were out of formation, and temporarily vulnerable. If Claudius had been in a position from where he could control his fleet, the battle may have turned into a Roman victory.
Instead, the ships at the head of the fleet, lacking any other orders, continued to sail into the harbour of Drepanum. Claudius sent a fast boat to order them back out to sea, but the damage was done. Several ships collided inside the harbour, suffering damage and lowering Roman morale even before the fighting had begun. The delay also gave Adherbal time to organise his fleet.
The two fleets lined up parallel to the coast. The Roman fleet had its back to the shore, and was close to dangerously to shallow water. The Carthaginian fleet had the advantage of open water, giving it more freedom to manoeuvre. When the fighting began, the Roman ships were unable to effectively help each other, while the Carthaginian ships had the freedom to pull back into the open sea or to help other ships that were hard pressed.
Eventually Claudius realised that the battle was lost. His position at the rear of the fleet meant that he was at the extreme left of the Roman line. This allowed him to escape, with the nearest thirty ships. This remnant of the fleet escaped back to the Roman camps outside Lilybaeum. Ninety-three ships were lost, along with most of their crews, taken prisoner by the Carthaginians having run aground.
Only part of the Roman fleet was lost at Drepanum. The rest was lost in a storm soon afterwards, while escorting a supply convoy to Lilybaeum. Having lost yet another fleet to bad weather, the Romans could no longer afford to replace the lost ships. It would be eight years before the Romans returned to the sea in strength.
With no fleets at sea, the Romans had little chance of capturing Lilybaeum or Drepanum. For the next two years they appear to have concentrated on keeping the Carthaginians pinned down on the west coast. They were helped in this by an apparent lack of interest in the war at Carthage in the period immediately after their victory at Drepanum. The appearance of a new Carthaginian commander on Sicily, Hamilcar Barca, in 247 B.C., gave a new lease of life to the Punic war effort, but even he was unable to seriously threaten the Roman position on the island.
Claudius was recalled to Rome and fined, reputedly for blasphemy. The case centred on the sacred chickens. These birds were carried onboard ship in cages. Before a battle grain was spread over the deck and the chickens released. If they ate, then the omens were good. Before Drepanum the chickens apparently did not eat. Claudius was said to have thrown them overboard, saying “if they will not eat, let them drink”.