Dromon

A dromon (from Greek δρόμων, "dromōn", "runner") was a type of galley and the most important warship of the Byzantine navy from the 5th to 12th centuries AD, when they were succeeded by Italian-style galleys. It was developed from the ancient liburnian, which was the mainstay of the Roman navy during the Empire.
Middle English "dromond" and Old French "dromont" are derived from the dromon, and described any particularly large medieval ship.
Evolution and features.
The appearance and evolution of medieval warships is a matter of debate and conjecture: until recently, no remains of an oared warship from either ancient or early medieval times had been found, and information had to be gathered by analyzing literary evidence, crude artistic depictions and the remains of a few merchant vessels (such as the 7th-century Pantano Longarini wreck from Sicily, the 7th-century Yassi Ada ship and the 11th-century Serçe Limanı wreck). Only in 2005–2006 did archaeological digs for the Marmaray project in the location of the Harbor of Theodosius (modern Yenikapi) uncover the remains of over 36 Byzantine ships from the 6th to 10th centuries, including four light galleys of the "galea" type.
The accepted view is that the main developments which differentiated the early dromons from the liburnians, and that henceforth characterized Mediterranean galleys, were the adoption of a full deck ("katastrōma"), the abandonment of the rams on the bow in favor of an above-water spur, and the gradual introduction of lateen sails. The exact reasons for the abandonment of the ram (, ) are unclear. Depictions of upward-pointing beaks in the 4th-century "Vatican Vergil" manuscript may well illustrate that the ram had already been replaced by a spur in late Roman galleys. One possibility is that the change occurred because of the gradual evolution of the ancient shell-first mortise and tenon hull construction method, against which rams had been designed, into the skeleton-first method, which produced a stronger and more flexible hull, less susceptible to ram attacks. Certainly by the early 7th century, the ram's original function had been forgotten, if we judge by Isidore of Seville's comments that they were used to protect against collision with underwater rocks. As for the lateen sail, various authors have in the past suggested that it was introduced into the Mediterranean by the Arabs, possibly with an ultimate origin in India. However, the discovery of new depictions and literary references in recent decades has led scholars to antedate the appearance of the lateen sail in the Levant to the late Hellenistic or early Roman period. Not only the triangular, but also the quadrilateral version were known, used for centuries (mostly on smaller craft) in parallel with square sails. 
Belisarius's fleet during the Vandalic War, as described by Procopius of Caesarea, was apparently at least partly fitted with lateen sails, making it probable that by that time the lateen had become the standard rig for the dromon, with the traditional square sail gradually falling from use in medieval navigation. These 6th-century dromons were single-banked ("monoreme") ships of probably 50 oars, arranged with 25 oars on each side. Again unlike Hellenistic vessels, which used an outrigger, these extended directly from the hull. In the later two-banked ("bireme") dromons of the 9th and 10th centuries, the two oar banks ("elasiai") were divided by the deck, with the first oar bank was situated below, whilst the second oar bank was situated above deck; these rowers were expected to fight alongside the ship's marines in boarding operations. The Greek scholar Christos Makrypoulias suggests an arrangement of 25 oarsmen beneath and 35 on the deck on either side for a dromon of 120 rowers. The overall length of these ships was probably about 32 meters. Although most contemporary vessels had a single mast ("histos" or "katartion"), the larger bireme dromons probably needed at least two masts in order to maneuver effectively, assuming that a single lateen sail for a ship this size would have reached unmanageable dimensions. The ship was steered by means of two quarter rudders at the stern ("prymnē"), which also housed a tent ("skēnē") that covered the captain's berth ("krab(b)at(t)os"). The prow ("prōra") featured an elevated forecastle ("pseudopation"), below which the siphon for the discharge of Greek fire projected, although secondary siphons could also be carried amidships on either side. A pavesade ("kastellōma"), on which marines could hang their shields, ran around the sides of the ship, providing protection to the deck crew. Larger ships also had wooden castles ("xylokastra") on either side between the masts, similar to those attested for the Roman liburnians, providing archers with elevated firing platforms. The bow spur ("peronion") was intended to ride over an enemy ship's oars, breaking them and rendering it helpless against missile fire and boarding actions.
The four "galeai" ships uncovered in the Yenikapi excavations, dating to the 10th–11th centuries, are of uniform design and construction, suggesting a centralized manufacturing process. They have a length of about , and are built of European Black Pine and Oriental plane.
Variants.
By the 10th century, there were three main classes of bireme warships of the general dromon type, as detailed in the inventories for the expeditions sent against the Emirate of Crete in 911 and 949: the "[chelandion] ousiakon" (), so named because it was manned by an "ousia" of 108 men; the "[chelandion] pamphylon" ([χελάνδιον] πάμφυλον), crewed with up to 120–160 men, its name either implying an origin in the region of Pamphylia as a transport ship or its crewing with "picked crews" (from , "all tribes"); and the "dromōn" proper, crewed by two "ousiai". In Constantine VII's "De Ceremoniis", the heavy "dromōn" is said to have an even larger crew of 230 rowers and 70 marines; the naval expert John H. Pryor considers them as supernumerary crews being carried aboard, while Makrypoulias suggests that the extra men correspond to a second rower on each of the upper-bank oars. A smaller, single-bank ship, the "monērēs" (μονήρης, "single-banked") or "galea" (γαλέα, from which the term "galley" derives), with ca. 60 men as crew, was used for scouting missions but also in the wings of the battle line.
Three-banked ("trireme") dromons are described in a 10th-century work dedicated to the "parakoimōmenos" Basil Lekapenos. However, this treatise, which survives only in fragments, draws heavily upon references on the appearance and construction of a classical Greek trireme, and must therefore be used with care when trying to apply it to the warships of the middle Byzantine period. The existence of trireme vessels is, however, attested in the Fatimid navy in the 11th and 12th centuries, and references made by Leo VI to large Arab ships in the 10th century may also indicate trireme galleys.
For cargo transport, the Byzantines usually commandeered ordinary merchantmen as transport ships ("phortēgoi") or supply ships ("skeuophora"). These appear to have been mostly sailing vessels, rather than oared. The Byzantines and Arabs also employed horse-transports ("hippagōga"), which were either sailing ships or galleys, the latter certainly modified to accommodate the horses. Given that the "chelandia" appear originally to have been oared horse-transports, this would imply differences in construction between the "chelandion" and the "dromōn" proper, terms which otherwise are often used indiscriminately in literary sources. While the "dromōn" was developed exclusively as a war galley, the "chelandion" would have had to have a special compartment amidships to accommodate a row of horses, increasing its beam and hold depth.