Decatur recruited her crew and procured her armament from Providence, Rhode Island, but by the beginning of August 1803 heavy and persistent rains had delayed her launching by two weeks.

She soon suffered a badly sprung bowsprit in exceptionally heavy seas, and Decatur put into Newport, Rhode Island, on 18 September 1803 to have it fixed, reasoning that repairs would be far easier in the United States than in the Mediterranean.

During the early part of 1804, she cruised the western Mediterranean in an unsuccessful search for a Tripolitan cruiser reportedly operating in that area.

Her boats captured a small sloop loaded with earthenware anchored close to the Tripoli coast on 30 April, 1804.

The bombardment was considerably less damaging to the defensive works protecting Tripoli than hoped for, though the American gunboat crews boarded and carried several of the Tripolitan vessels sent out to engage them.

When Intrepid blew up prematurely, killing her entire crew, Argus remained there to pick up survivors, but none had appeared by sunrise when she returned to her blockade station.

During the preceding months, she had made several voyages to Egypt in support of Consul William Eaton's efforts to raise a force of men to take Derna in conjunction with the deposed pasha.

After a march of over 600 miles (970 km) across the Libyan Desert in what is now Libya, the polyglot army – there were only 10 Americans in the whole force – arrived at Derna on 25 April 1805.

A desperate charge led by United States Marine Corps Lieutenant Presley O'Bannon managed to carry the gun batteries by storm and breathed new life into the assault.

After hoisting the American flag over the battlements, O'Bannon ordered the already loaded captured guns to be turned on the town.

After Eaton's and O'Bannon's victory, a Tripolitan army, which had been sent to reinforce the town, arrived and began preparations to retake Derna.

When the Tripolitans finally assaulted the town on 13 May 1805, Argus joined in the fray and enabled the defensive forces narrowly to beat back the charging enemy troops.

Between that time and early June 1805, the Tripolitans made a few more half-hearted approaches during which Argus's long 12-pounders (5 kg) came into play.

The troops and the deposed pasha were embarked in Constellation that evening, and Argus and the other American ships quit the area.

During one cruise between 8 October 1812 and 3 January 1813, she captured six valuable prizes and eluded an entire British squadron during a three-day stern chase.

[9] Through clever handling, she even managed to take one of the prizes as she was fleeing from the overwhelmingly superior British force.

The British brig-sloop HMS Pelican had just arrived in Cork Harbour in Ireland, having escorted a convoy from the West Indies, and immediately put to sea again on 10 August 1813.

Both American[10] and British[13] historians have suggested that Argus's crew looted some of the cargo, and that their debauched state affected their performance during the coming battle with Pelican.

As with Argus's previous captures, the Americans set fire to the prize; unfortunately for them, Pelican was near enough to sight the smoke from the burning vessel and make for it.

At 05:00 on the morning of 14 August 1813, Argus and Pelican sighted each other five leagues (about 15 miles) west of St David's Head.

Finally, three-quarters of an hour after the action began, the two vessels came into contact, Argus's bow against Pelican's quarter.