Meanwhile, "Philadelphia" lay in Tripoli Harbor threatening to become Tripoli's largest and most powerful corsair. Preble decided that he must destroy the frigate before the enemy could fit her out for action against his squadron. In order to take the Tripolitans by surprise, he assigned the task to the only ship which could be sure of passing as a North African vessel, "Intrepid". He appointed Lieutenant Stephen Decatur captain of the ketch on 31 January 1804 and ordered him to prepare her for a month's cruise to Tripoli in company with . Preble's orders directed Decatur to slip into harbor at night, to board and burn the frigate, and make good his retreat in "Intrepid", unless it then seemed feasible to use her as a fire ship against other shipping in the harbor. In the latter case, he was to escape in boats to "Syren" which would await just outside the harbor.