The Roman Civil War (49–45 BC) pitted Julius Caesar against Pompey the Great and the conservative senatorial faction. While Caesar’s land campaigns—especially the lightning invasion of Italy and the decisive victory at Pharsalus—dominate historical memory, his naval operations were equally critical. Control of the Mediterranean sea lanes determined supply lines, troop movements, and the ability to besiege coastal cities. Caesar not only had to improvise a fleet but also to outmanoeuvre a Pompeian navy that had dominated the sea for years. His naval battles, though less famous than those of the Punic Wars, were masterclasses in strategic adaptation and tactical innovation.

Strategic Context: The Struggle for the Mediterranean

When Caesar crossed the Rubicon in 49 BC, he controlled a veteran army but almost no ships. Pompey, by contrast, held the loyalty of most of the Roman navy, the major eastern provinces, and the grain-supplying regions of Africa and Sicily. To defeat Pompey, Caesar had to secure his rear in Italy, transport armies across the Adriatic, and ultimately isolate his rival from naval reinforcement. This required either swiftly building a fleet or capturing enemy vessels—or both.

Caesar’s initial strategy was to seize key ports and naval stores in Italy and Gaul. He also requisitioned ships from allied cities and impressed merchant vessels. The result was a hastily assembled navy that often faced more experienced Pompeian crews. Nevertheless, Caesar’s relentless energy, his habit of rewarding initiative among centurions and sailors, and his willingness to risk engagement at unfavourable odds repeatedly turned the tide.

Early Naval Clashes: The Battle of Mylae (49 BC)

The first significant naval engagement of the war occurred near Mylae (modern Milazzo) on the north coast of Sicily. During Caesar’s campaign to secure the island and its grain supply, his legate Gaius Scribonius Curio led a mixed force of transports and warships. The Pompeian commander, Lucius Nasidius, sailed from Messana with a fleet of quinqueremes to challenge the Caesarian squadron.

The battle was fought in shallow coastal waters, limiting the manoeuvrability of the heavier Pompeian ships. Caesar’s vessels, many of them converted merchantmen, relied on boarding rather than ramming. According to Caesar’s own account in The Civil War, his sailors used grappling hooks and boarding bridges—a tactic Caesar had earlier used against the Veneti in Gaul—to turn the engagement into a land fight at sea. The result was a decisive Caesarian victory. Nasidius retreated, and Curio was able to capture the strategic city of Messana, securing Sicily for Caesar.

The Battle of Mylae demonstrated that Caesar’s naval forces, though improvised, could defeat Pompeian squadrons through aggressive boarding tactics. It also gave Caesar a base to threaten Africa and to protect the grain shipments vital to Rome.

The Sicilian Campaign and Its Aftermath

While Mylae was a tactical triumph, it did not eliminate the Pompeian naval threat. Curio soon launched an invasion of Africa but was defeated and killed at the Battle of the Bagradas River. The loss of Curio and his army was a severe blow, partly because Caesar lacked the naval transport to rescue the survivors. This setback underscored the need for a more permanent fleet and a comprehensive maritime strategy.

The Siege of Massilia: Naval Blockade and the Battle of Tauroentum

One of the most complex naval operations of the civil war occurred at Massilia (modern Marseille). This wealthy Greek city-state, nominally allied to Rome, sided with Pompey. Caesar could not afford to leave a hostile port on his flank while he marched into Spain. He besieged Massilia by land and sea, but the city possessed a strong fleet of its own.

Caesar ordered the construction of a fleet at Arelate (Arles) using timber felled from the region. In a remarkable feat of rapid shipbuilding, his legates Decimus Brutus and Gaius Trebonius assembled a squadron of warships—many of them modified to carry extra marines and boarding equipment. Meanwhile, the Massiliot fleet, reinforced by Pompeian ships under Nasidius, attempted to break the blockade.

The Battle of Tauroentum (49 BC)

The first naval engagement took place off Tauroentum (near modern Le Cros-de-Cagnes). Decimus Brutus commanded the Caesarian fleet, which consisted of about 12 galleys against a larger enemy force. Again, Caesar’s tactics favoured boarding. The Caesarian ships used corvi (boarding bridges) to entangle and capture the enemy vessels. The battle was fierce, and the Massiliot admiral was killed. Despite being outnumbered, the Caesarian fleet prevailed, capturing or sinking many ships and forcing the remnants to retreat to Spain.

The blockade tightened. A second naval battle near Massilia itself saw the remaining Pompeian-Massiliot fleet destroyed. The city surrendered after a protracted siege, and Caesar pardoned the inhabitants, a gesture of clemency that became a hallmark of his rule.

The naval battles at Massilia demonstrated Caesar’s ability to improvise a shipyard and train crews under pressure. They also protected his line of communication with Italy while he campaigned in the Iberian Peninsula.

The Battle of Drepana (49 BC? Separating Fact from Fiction)

The original article references a “Battle of Drepana” in 49 BC, but historical sources are inconsistent. The famous Battle of Drepana occurred in 249 BC during the First Punic War. In the civil war, a naval skirmish near Drepana (modern Trapani, Sicily) may have occurred as part of the operations to secure western Sicily—possibly during the campaign of Curio or later when Caesar’s governor Aulus Allienus moved troops to support the African War. However, no major engagement by that name stands out in the records. It is possible that the battle was a minor encounter that later sources conflated with the Punic War battle, or it may refer to a small, unrecorded action.

What is clear is that Caesar’s forces maintained control of Sicilian waters after Mylae, and Drepana, as the westernmost port of Sicily, would have been a contested point. The Caesarian fleet’s ability to patrol the straits of Messina and prevent Pompeian raids was key to holding the island.

To avoid confusion, the more significant naval actions (Mylae, Massilia, and later the Adriatic crossings) deserve emphasis. The name “Drepana” likely reflects a local engagement that did not alter the strategic balance.

Caesar’s Naval Strategies: Innovation and Resourcefulness

Caesar’s success at sea was not due to superior ships but to superior leadership and logistics. He consistently used boarding tactics to negate the enemy’s advantage in seamanship. He also mastered the art of rapid shipbuilding: when he needed a fleet to pursue Pompey’s fleet across the Adriatic, he ordered ships to be constructed in Italian ports within weeks.

Ship Design and Tactics

Roman warships of the late Republic were usually triremes or quinqueremes—oared galleys with a bronze ram at the bow. Caesar’s innovations included adding more marines, fitting boarding towers, and using grappling hooks. He adapted the corvus (boarding bridge) that had been used in the First Punic War but which had fallen out of favour because of its instability in rough seas. In calm coastal waters or in harbours, however, it proved devastating.

He also employed small, fast liburnian vessels for scouting and dispatch, and he understood the importance of coastal fortifications covering harbours. His siege of Massilia involved building a mole (breakwater) to block the harbour mouth, forcing the enemy to fight outside their own walls.

Logistics and Supply

Naval logistics were Caesar’s greatest challenge. He had to transport legions from Brundisium (Brindisi) to Epirus across the Adriatic, a dangerous passage even in peacetime. Pompey had a larger fleet, commanded by the capable Marcus Calpurnius Bibulus, who attempted to blockade the Italian coast. Caesar’s answer was to cross in winter, when storms kept the Pompeian fleet in harbour. He repeatedly ran the blockade, losing some transports but landing the core of his army in Greece.

Later, when his lieutenant Gaius Antonius (brother of Mark Antony) was trapped at Curicta (Krk), Caesar’s naval forces attempted a rescue. The failure at Curicta showed the limits of his improvisation, but it also taught lessons that he applied at the Battle of Pharsalus—where Pompey’s fleet never seriously intervened because it lacked the supply bases to maintain a close watch on the coast.

Impact on the Civil War Outcome

The naval battles led by Caesar, often fought by his legates but under his overall direction, had three major strategic effects:

  • Secure supply lines: Control of Sicily, Sardinia, and Gaul ensured grain fed Rome and Caesar’s armies.
  • Isolation of Pompey: By blocking Pompey’s ability to reinforce Greece from Spain and Africa, Caesar concentrated his land forces for the decisive battle.
  • Psychological dominance: Caesar’s reputation for speed and audacity extended to the sea. Pompey’s admirals became cautious, unwilling to risk engagement, which allowed Caesar to transport troops with relative impunity once he gained a foothold in the East.

After Pharsalus, the naval war effectively ended. Pompey was murdered in Egypt, and the remaining Pompeian fleet either surrendered or was destroyed in the later African campaigns under Scipio and Cato. Caesar’s final victory at Thapsus (46 BC) and Munda (45 BC) were land battles, but they were made possible by the naval control he had established in the preceding years.

Later Naval Operations Under Caesar’s Command

Even after defeating Pompey, Caesar conducted naval campaigns against the Egyptian fleet in Alexandria (48–47 BC) and against Pharnaces of Pontus at the coast of Pontus (47 BC). The Alexandrian War involved desperate street fighting alongside naval skirmishes, where Caesar’s ships—again, slower but packed with legionaries—fended off Egyptian galleys. He famously set fire to the Egyptian fleet in the harbour, a blaze that accidentally spread to the famous Library of Alexandria. While the loss was tragic, the tactical necessity was clear: Caesar needed to break the naval siege that trapped him in the palace quarter.

The Battle of the Nile (47 BC)

On the Nile, Caesar defeated the Egyptian army of Ptolemy XIII, but the naval action had already forced the Egyptian fleet to withdraw. This battle ended the Ptolemaic rebellion and installed Cleopatra as queen.

Campaign Against Pharnaces

At Zela, Caesar famously declared “Veni, vidi, vici.” But before that, he had destroyed Pharnaces’ fleet near the coast of the Black Sea, using his usual boarding tactics. The quick victory freed him to return to Rome and settle the civil war in the West.

Legacy of Caesar’s Naval Wars

Julius Caesar was not a professional admiral, but his naval battles during the civil war reveal a commander who could adapt to any environment. He understood that sea power was not about winning grand fleet actions but about enabling land operations—transport, supply, blockade. His improvisation, from building ships in Gaul to boarding tactics, set a precedent for later Roman naval warfare under Augustus and his successors.

The lessons learned in the civil war—the importance of well-trained marines, the value of small, fast liburnians over heavy quinqueremes, and the need for secure ports—helped shape the Roman imperial navy. Augustus, after Actium, would create a standing fleet based on liburnian designs, a direct evolution of Caesar’s wartime experiments.

Why History Overlooks Caesar’s Naval Battles

Part of the reason Caesar’s naval exploits are underrated is that he described them in his own commentaries with characteristic brevity. He was far more interested in recounting his land victories. But modern historians have re-evaluated these engagements. The Livius.org article on the civil war notes that Caesar’s ability to move armies across the Mediterranean was “his most underappreciated skill.” A study by the World History Encyclopedia highlights how his shipbuilding at Arelate was “a logistical miracle.”

For those who want to dive deeper, the UNRV history page on the civil war provides a detailed timeline of the naval movements. A scholarly assessment can be found in JSTOR’s article “Caesar and the Sea” by Philip Sabin (registration may be required). Finally, a modern tactical analysis of the Massilia siege appears in an academic paper on Academia.edu.

Conclusion: The Admiral Who Never Wanted to Be One

Julius Caesar’s naval battles during the Roman Civil War were fought out of necessity, not preference. He would rather have marched his legions across the Alps than sail across the Adriatic in winter. Yet when the situation demanded, he built fleets, trained crews, and engaged the enemy with the same aggression and cunning he showed on land. The battles of Mylae, Massilia, and the dangerous Adriatic crossings were not decisive in themselves, but they created the conditions for the decisive land battles. Without them, Caesar might never have landed in Greece, never defeated Pompey, and the history of Rome—and the world—would have been entirely different.