A Roman legion (from Latin "legio" "military levy, conscription", from "legere" "to choose") was the largest unit of the Roman army, evolving from 3000 men in early times to over 5200 men in imperial times, consisting of "centuries" as the basic units.
 Until the middle of the first century, 10 cohorts (about 5,000 men) made up a Roman Legion.
 This was later changed to nine cohorts of standard size (with 6 centuries at 80 men each) and one cohort, the first cohort, of double strength (5 double-strength centuries with 160 men each).
The Byzantine army or Eastern Roman army was the primary military body of the Byzantine armed forces, serving alongside the Byzantine navy.
 A direct continuation of the Roman army, the Eastern Roman army maintained a similar level of discipline, strategic prowess and organization.
 It was among the most effective armies of western Eurasia for much of the Middle Ages.
 Over time the cavalry arm became more prominent in the Byzantine army as the legion system disappeared in the early 7th century.
 Later reforms reflected some Germanic and Asian influences – rival forces frequently became sources of mercenary units e.g.; Huns, Cumans, Alans and (following the Battle of Manzikert) Turks, meeting the Empire's demand for light cavalry mercenaries.
 Since much of the Byzantine military focused on the strategy and skill of generals utilizing militia troops, heavy infantry were recruited from Frankish and later Varangian mercenaries.
Legio secunda adiutrix ("Rescuer Second Legion"), was a legion of the Imperial Roman army founded in AD 70 by the emperor Vespasian (r. 69-79), originally composed of Roman navy marines of the "classis Ravennatis".
 There are still records of II "Adiutrix" in the Rhine border in the beginning of the 4th century.
 The legion's symbols were a Capricorn and Pegasus.
The Batavi was an "auxilia palatina" (infantry) unit of the Late Roman army, active between the 4th and the 5th century.
 It was composed by 500 soldiers and was the heir of those ethnic groups that were initially used as auxiliary units of the Roman army and later integrated in the Roman Empire after the "Constitutio Antoniniana".
 Their name was derived from the people of the Batavi.
The structural history of the Roman military concerns the major transformations in the organization and constitution of ancient Rome's armed forces, "the most effective and long-lived military institution known to history."
 From its origins around 800 BC to its final dissolution in AD 476 with the demise of the Western Roman Empire, Rome's military organization underwent substantial structural change.
 At the highest level of structure, the forces were split into the Roman Army and the Roman Navy, although these two branches were less distinct than in many modern national defense forces.
 Within the top levels of both army and navy, structural changes occurred as a result of both positive military reform and organic structural evolution.
 These changes can be divided into four distinct phases.
A centurion (Latin: "centurio" ; Greek: κεντυρίων , "kentyríōn", or ἑκατόνταρχος , "hekatóntarkhos") was a professional officer of the Roman army after the Marian reforms of 107 BC.
 Most centurions commanded groups of centuries of around 80 men but senior centurions commanded cohorts or took senior staff roles in their legion.
 Centurions were also found in the Roman navy.
 In the Byzantine Army, they are also known by the name kentarch (κένταρχος , "kentarchos").
 Their symbol of office was the vine staff, with which they disciplined even Roman citizens protected from other forms of beating by the Porcian Laws.
The Heruli was an "auxilia palatina" unit of the Late Roman army, active between the 4th and the 5th century.
 It was composed of 500 soldiers and was the heir of those ethnic groups that were initially used as auxiliary units of the Roman army and later integrated in the Roman Empire after the "Constitutio Antoniniana".
 Their name was derived from the people of the Heruli.
 In the sources they are usually recorded together with the "Batavi", and it is probable the two units fought together.
 At the beginning of the 5th century two related units are attested, the Heruli seniores in the West and the Heruli iuniores in the East.
The Roman navy (Latin: "Classis" , lit.
 "fleet") comprised the naval forces of the Ancient Roman state.
 The navy was instrumental in the Roman conquest of the Mediterranean basin, but it never enjoyed the prestige of the Roman legions. Throughout their history, the Romans remained a primarily land-based people and relied partially on their more nautically inclined subjects, such as the Greeks and the Egyptians, to build their ships.
 Because of that, the navy was never completely embraced by the Roman state, and deemed somewhat "un-Roman".
In modern scholarship, the "late" period of the Roman army begins with the accession of the Emperor Diocletian in AD 284, and ends in 476 with the deposition of Romulus Augustulus, being roughly coterminous with the Dominate.
 During the period 395–476, the army of the Roman Empire's western half progressively disintegrated, while its counterpart in the East, known as the East Roman army (or the early Byzantine army) remained largely intact in size and structure until the reign of Justinian I (r. AD 527–565).
The East Roman army refers to the army of the Eastern section of the Roman Empire, from the empire's definitive split in 395 AD to the army's reorganization by themes after the permanent loss of Syria, Palestine and Egypt to the Arabs in the 7th century during the Byzantine-Arab Wars.
 The "East Roman army" is the continuation of the Late Roman army of the 4th century until the Byzantine army of the 7th century onwards.

Question: What unit from the Roman Army consisting of centuries enjoyed more prestige than the Roman navy?
Answer: Roman legion