A Roman Bireme

A Roman bireme - From helenistic Era

The generic Roman term for an oar-driven galley warship was "long ship" (Latin: navis longa, Greek: naus makra), as opposed to the sail-driven navis oneraria, a merchant vessel, or the minor craft (navigia minora) like the scapha.

The navy consisted of a wide variety of different classes of warships, from heavy polyremes to light raiding and scouting vessels. Unlike the rich Hellenistic Successor kingdoms in the East however, the Romans did not rely on heavy warships, with quinqueremes (Gk. pentērēs), and to a lesser extent quadriremes (Gk. tetrērēs) and triremes (Gk. triērēs) providing the mainstay of the Roman fleets from the Punic Wars to the end of the Civil Wars. The heaviest vessel mentioned in Roman fleets during this period was the hexareme, of which a few were used as flagships. Lighter vessels such as the liburnians and the hemiolia, both swift types invented by pirates, were also adopted as scouts and light transport vessels.

During the final confrontation between Octavian and Mark Antony, Octavian's fleet was composed of quinqueremes, together with some "sixes" and many triremes and liburnians, while Antony, who had the resources of Ptolemaic Egypt to draw upon, fielded a fleet also mostly composed of quinquiremes, but with a sizeable complement of heavier warships, ranging from "sixes" to "tens" (Gk. dekērēs). Later historical tradition made much of the prevalence of lighter and swifter vessels in Octavian's fleet, with Vegetius even explicitly ascribing Octavian's victory to the liburnians


This prominence of lighter craft in the historical narrative is perhaps best explained in light of subsequent developments. After Actium, the operational landscape had changed: for the remainder of the Principate, no opponent existed to challenge Roman naval hegemony, and no massed naval confrontation was likely. The tasks at hand for the Roman navy were now the policing of the Mediterranean waterways and the border rivers, suppression of piracy, and escort duties for the grain shipments to Rome and for imperial army expeditions. Lighter ships were far better suited to these tasks, and after the reorganization of the fleet following Actium, the largest ship kept in service was a hexareme, the flagship of the Classis Misenensis. The bulk of the fleets was composed of the lighter triremes and liburnians (Latin: liburna, Greek: libyrnis), with the latter apparently providing the majority of the provincial fleets. In time, the term "liburnian" came to mean "warship" in a generic sense.

In addition, there were smaller oared vessels, such as the navis actuaria, with 30 oars (15 on each bank), a ship primarily used for transport in coastal and fluvial operations, for which its shallow draught and flat keel were ideal. In late Antiquity, it was succeeded in this role by the navis lusoria ("playful ship"), which was extensively used for patrols and raids by the legionary flotillas in the Rhine and Danube frontiers.

Roman ships were commonly named after gods (Mars, Iuppiter, Minerva, Isis), mythological heroes (Hercules), geographical maritime features such as Rhenus or Oceanus, concepts such as Harmony, Peace, Loyalty, Victory (Concordia, Pax, Fides, Victoria) or after important events (Dacicus for the Trajan's Dacian Wars or Salamina for the Battle of Salamis). They were distinguished by their figurehead (insigne or parasemum), and, during the Civil Wars at least, by the paint schemes on their turrets, which varied according to each fleet

Armament and tactics

Ballistae on a Roman ship

In Classical Antiquity, a ship's main weapon was the ram (rostra, hence the name navis rostrata for a warship), which was used to sink or immobilize an enemy ship by holing its hull. Its use, however, required a skilled and experienced crew and a fast and agile ship like a trireme or quinquereme. In the Hellenistic period, the larger navies came instead to rely on greater vessels. This had several advantages: the heavier and sturdier construction lessened the effects of ramming, and the greater space and stability of the vessels allowed the transport not only of more marines, but also the placement of deck-mounted ballistae and catapults. Although the ram continued to be a standard feature of all warships and ramming the standard mode of attack, these developments transformed the role of a warship: from the old "manned missile", designed to sink enemy ships, they became mobile artillery platforms, which engaged in missile exchange and boarding actions. The Romans in particular, being initially inexperienced at sea combat, relied upon boarding actions through the use of the corvus. Although it brought them some decisive victories, it was discontinued because it tended to unbalance the quinqueremes in high seas; two Roman fleets are recorded to have been lost during storms in the First Punic War.

During the Civil Wars, a number of technical innovations, which are attributed to Agrippa, took place: the harpax, a catapult-fired grappling hook, which was used to clamp onto an enemy ship, reel it in and board it, in a much more efficient way than with the old corvus, and the use of collapsible fighting towers placed one apiece bow and stern, which were used to provide the boarders with supporting fire