How big is a legion
Size of the Roman army
Roman Army Structure - Vindolanda Museumhow
By the size of the Roman army is meant the changes increases and reductions in the number of its contingents: legions , auxiliaries , Praetorian cohorts , Urban cohorts , vigiles , and naval forces over the course of twelve centuries - from BC to AD the Fall of the Western Roman Empire. After the founding of Rome, legend has it that the first king, Romulus established the original Roman legion with 3, soldiers and cavalry ,  which might have been doubled when the city of Rome was expanded by union with the Sabines , coming to a total of 6, infantry and cavalry. We know from Livy that at the time of the Latin War BC there were normally two armies enlisted, composed of two legions of 4,, infantry and cavalry each, for a total armed force of 16,, infantry and 1, cavalry. At the time of the Pyrrhic War , the Roman army in the field consisted of four armies,  each of which contained two legions of Roman citizens and two units of allies. Each legion consisted of 4,, infantry  and cavalry,  while the allied units had an equal number of infantry but three times as many cavalry cavalry per unit. Around the middle of the third century BC, the Roman army consisted of an occupation force in Sicily and Tarentum two legions of 4, infantry and cavalry each , two consulary armies both composed of two reinforced legions of around 5, infantry and cavalry each and about 30, allied soldiers including 2, cavalry in permanent active service, with another 90, in reserve, ready to intervene if necessary and made up of 50, Etruscans and Sabines including 4, cavalry , 20, Umbrians and Sarsinans , 20, Veneti and Cenomani. The complete armed forces, therefore, could have reached , individuals, of which only 30, were Romans 6 legions.
A Roman legion Latin romanum legio from legio "military levy, conscription ", from legere "to choose" was a large military unit of the Roman army. In the early Roman Kingdom "legion" may have meant the entire Roman army but sources on this period are few and unreliable. During much of the republican era , a legion was divided into three lines of ten maniples. In the late republic and much of the imperial period from about BC , a legion was divided into ten cohorts , each of six or five centuries. Legions also included a small ala , or cavalry, unit. By the third century AD, the legion was a much smaller unit of about 1, to 1, men, and there were more of them.
Members of the st Legion. A legion was a military unit. Typically, the term indicated a large-scale formation comparable to a division or battlegroup , consisting of several regiments and comprising about ten thousand fighting troops. The Legion was not a standard element in the line Army forces of either the Galactic Republic or Galactic Empire , which identified comparable formations as divisions and battlegroups. It was, however, a key field formation for the white-armored clone troopers of the Grand Army of the Republic and their successors, the Stormtrooper Corps of the Galactic Empire. A clone legion consisted of 9, troops, normally headed by a Jedi General and a Senior clone commander.
Legion , a military organization, originally the largest permanent organization in the armies of ancient Rome. The term legion also denotes the military system by which imperial Rome conquered and ruled the ancient world. The expanding early Roman Republic found the Greek phalanx formation too unwieldy for fragmented fighting in the hills and valleys of central Italy. Accordingly, the Romans evolved a new tactical system based on small and supple infantry units called maniples. Each maniple numbered men in 12 files and 10 ranks. Maniples drew up for battle in three lines, each line made up of 10 maniples and the whole arranged in a checkerboard pattern. Conversely, the second line could merge with the first to form a solid front 10 ranks deep and m 1, feet wide.
Roman legions varied over time not only in size but in number. In an article estimating population size in ancient Rome, Lorne H. Ward comments that in the early, close-to-annual border skirmishes, only the number of men in half a conventional legion might be deployed. The Roman armies exercitus were composed mainly of Roman legions from the time of the legendary reforms of King Servius Tullius [also see Mommsen], according to ancient historians Cary and Scullard. The name for the legions comes from the word for the levy legio from a Latin verb for 'to choose' [ legere ] that was made on the basis of wealth, in the new tribes Tullius is also supposed to have created. Each legion was to have 60 centuries of infantry. A century is literally elsewhere, you see a century in the context of years , so the legion would have originally had infantrymen.
Roman Battle Tactics
The Varied Size of the Roman Legions