Under Augustus, the Imperial Roman legion became a permanent unit of about 5,200 heavy infantry, staffed by entirely professional soldiers on standard 25-year terms. He also fixed the number of legions at 28, having inherited over 50 after his defeat of Mark Anthony, although 3 were destroyed in the Varian Disaster. Under Septimius Severus, this number had grown to 30 legions of 5,600 heavy infantry.
Organisation
A legion was divided into ten cohorts, each of six centuries, with a small force of cavalry (eques legionis) attached to it used as messengers and scouts.
The cohort (cohors) was made up of 480 men in 6 centuries, with the first century being double-strength. The century (centuria) was made up of 80 men in 10 contubernia, or tent-groups. The contubernium was made up of 8 men.
The legion was commanded by a Legionary Legate (legatus legionis), supported by a Broad-Stripe Tribune (tribunus laticlavius), 5 Narrow-Stripe Tribunes (tribuni angusticlavii) and a Camp Prefect (praefectus castrorum). Each cohort and century was commanded by a centurion (centurio), with an optio as his second in command.
See Ranks of the Roman Army for more detail.
A legion was always supported by the Auxilia, non-citizen units, who normally matched the legion in strength.
Equipment
A legionary was expected to carry a great deal of equipment with him whilst on campaign; not only his weapons and armour but also his clothes, cooking utensils and tools for camp construction.
He was armed with a gladius, a pugio and two pila, while wearing a galea and lorica segmentata and carrying a scutum.
Aside from the weapons and armour, a legionary would carry such items as a pickaxe, a saw, a sickle, a shovel, a waterskin, a wicker basket and more, which would have been carried on a forked pole. This was first introduced by the concsul C. Marius in 107 BC and earned his men the nickname Marius’ Mules.
See Equipment of the Roman Army for more detail.
List of Imperial Legions
| I Adiutrix I Germanica I Italica I Minervia I Parthica II Adiutrix II Augusta II Italica II Parthica II Traiana Fortis III Augusta III Cyrenaica III Gallica III Italica III Parthica IV Flavia Felix IV Macedonica IV Scythica V Alaudae V Macedonica VI Ferrata VI Victrix | VII Claudia VII Gemina VIII Augusta IX Hispana X Fretensis X Gemina XI Claudia XII Fulminata XIII Gemina XIV Gemina XV Apollinaris XV Primigenia XVI Flavia Firma XVI Gallica XVII XVIII XIX XX Valeria Victrix XXI Rapax XXII Deiotariana XXII Primigenia XXX Ulpia Victrix |
Digital Maps of the Ancient World 