At the close of the First Punic War (241 BC), Rome had at its disposal a considerable navy left over from that epic conflict. The navy was employed in smaller conflicts in the following years, but not until Pompey's anti-piracy campaign of 67 BCE was it again employed in such large and sustained actions. In 238 BC, the Romans annexed Sardinia and Corsica (Thiel, p343), the occupation and pacification of which would have required a fleet, if in no other capacity than to transport soldiers to the islands. Thiel points out that it served as a "fleet in being," (p350) a strong presence which discouraged resistance, comparable to America's Great White Fleet of the late 19th century CE. Around the same time, the Senate ordered a campaign against the pirates of Liguria, an area in the northwest of Italy. This was undertaken, so far as I can determine, mostly on land, but showed concern for naval interests.
A more substantial operation was undertaken by the Romans against the Illyrians beginning in 230 BC (Polybius, II.8). Between 233 and 231, the Illyrian king Agron had gathered stronger land and naval forces than any prior king of that country (Polybius, II.2.4). The Greek historian Polybius gives the number of the fleet as 100, and refers to the ships as lemboi, or lembi in Latin. These, the native ships of the piratical Illyrians, had wider beams than typical warships of the day and lacked rams (Torr, p. 115). After hearing of his success against the Aetolians, Agron made so merry that he caught a cough and died, according to Polybius. He was succeeded by his wife Teuta, who sanctioned extensive privateer activity and authorized her commanders to use their substantial forces to attack, besiege, pillage, or plunder as they pleased. Epirus was plundered in this way. The Illyrian pirates stepped up their attacks on Italian merchants, and repeated protests by the latter brought the matter to the attention of the Roman Senate.
The senators dispatched two envoys, Gaius and Lucius Coruncanius, to Queen Teuta. Receiving the Romans haughtily, the queen guaranteed only that the official forces of Illyria would make no attacks; she was not responsible for the actions of privateers. One of the envoys responded angrily, and for this Teuta had him killed on his return voyage (Polybius, II.8). This did not go over well with the Roman people, who consented to the raising of an expedition. Thiel presents the case that the Senate had not ignored the piratical practices of the Illyrians because of their own indifference, but rather because they were hamstrung without the approval of the comitia centuriata. This assembly, responsible for discussing and confirming military matters, was firmly in the hands of the plebeians, or lower-class citizens, who were wary of military operations outside of Italy (Thiel, pp. 344-5). Consequently, the Senate had to wait until the increased attacks created a situation severe enough to draw the attention of the plebs. The murder of Coruncanius shifted the popular opinion in favor of war. Thiel further points out that this was an opportune time for the Romans to go to war, as the Macedonians, Illyria's chief allies, were occupied with important matters elsewhere.
In 229 BC, the consul Gnaeus Fulvius set off for Illyria with 200 quinqueremes, while his counterpart Aulus Postumius took the soldiers. Fulvius first set out for Corcyra, with hopes of relieving the siege by the Illyrian forces there. He was too late, but the commander of the Illyrian garrison on Corcyra, Demetrius of Pharos, turned the island over to the consul. It was placed under Roman protection. Fulvius and the fleet joined Postumius and the army at Apollonia, and the Romans proceeded north, up the coast of Illyria, causing the Illyrians to abandon the sieges of Epidamnus and Issa, placing both of those cities under their protection. On the way, the fleet captured twenty lembi carrying off food in order to save it from capture (Polybius, II.11.14), also subduing several coastal settlements. Teuta withdrew to her fortress at Rhizon for the winter, while the Romans left 40 ships under Postumius at Epidamnus. The following spring, in 228 BC, the queen sued for peace and gained it, giving up in return portions of her kingdom, an amount of tribute to Rome, and the right to sail south of Lissus with more than two unarmed vessels (ibid. II.12.3). Rome retained control of 120 miles of Illyrian coast, from Lissos to Epirus, and set up Demetrius of Pharos with a client kingdom north of Teuta's (Thiel, p. 354). Thiel explains that the former act was not so much to chastise Illyria as to provide a barrier between Macedon and the sea. Roman policy was decidedly anti-Macedon during this time, and the latter country would ally with Hannibal during the Second Punic War.
After this, the First Illyrian war, the Romans had to contend with a major invasion of the Gauls, which they successfully drove off. They were then faced with the appointment of Hannibal as Carthaginian commander in Spain and his subsequent attack on Saguntum. Encouraged by these perceived weaknesses in Roman power, the Illyrian Demetrius of Pharos raised a fleet of 90 lembi and sailed south of Lissos, in violation of the treaty. He made several unsuccessful attacks on Pylos and then, taking 50 of the ships, began pillaging the Cyclades (Polybius, III.16.3-4). The Romans responded quickly, hoping to put out the Illyrian fire before Hannibal could bring the Carthaginian torch to bear, and sent Lucius Aemilius across the Adriatic in 219 BC. The fleet quickly captured Dimale, previously regarded as impregnable, and moved toward Pharos, where Demetrius had encamped. Aemilius detached 20 of his ships to make a show in Pharos' harbor, while the rest of the fleet secretly landed its troops behind the town. Demetrius sent his garrison out to meet the perceived threat of the 20 ships, and at that time the concealed Romans attacked his rear. The battle was decided in Rome's favor, and Demetrius barely escaped on a lembus to his benefactor Philip of Macedon. The Romans returned to Italy to face Hannibal, leaving unscathed Demetrius' ally Scerdilaidas and concluding the Second Illyrian War.Works Cited: