The war continued, with neither side able to gain a decisive advantage. The Carthaginians attacked and recaptured Akragas in 255 BC, but not believing they could hold the city, they razed and abandoned it. The Romans rapidly rebuilt their fleet, adding 220 new ships, and captured Panormus (modern Palermo) in 254 BC. The next year they lost 150 ships to a storm. In 251 BC the Carthaginians attempted to recapture Panormus, but were defeated in a battle outside the walls. Slowly the Romans had occupied most of Sicily; in 249 BC they besieged the last two Carthaginian strongholdsin the extreme west. They also launched a surprise attack on the Carthaginian fleet, but were defeated at the Battle of Drepana. The Carthaginians followed up their victory and most of the remaining Roman warships were lost at the Battle of Phintias. After several years of stalemate, the Romans rebuilt their fleet again in 243 BC and effectively blockaded the Carthaginian garrisons. Carthage assembled a fleet which attempted to relieve them, but it was destroyed at the Battle of the Aegates Islands in 241 BC, forcing the cut-off Carthaginian troops on Sicily to negotiate for peace.