The Legions of Rome

The Roman legions were first established during the Roman Republic, which lasted from 509 BCE to 27 BCE. It is believed that the first Roman legion, the Legio I, was established by the Roman king Servius Tullius in the 6th century BCE. However, the Roman Republic’s military system was not solely based on the legions, and it relied on a mix of different units, including cavalry, archers, and skirmishers.

It was during the Roman Republic’s later period, particularly in the 3rd and 2nd centuries BCE, that the Roman legions became the dominant military force of Rome. During this time, the legions evolved into a standardized, professional standing army consisting of heavy infantry soldiers, trained and equipped to fight in a particular formation, known as the manipular formation.

The Roman legions continued to be the backbone of the Roman military throughout the Roman Empire’s history, which lasted from 27 BCE to 476 CE. The legions were gradually replaced by other military units, such as the comitatenses and the limitanei, as the Roman Empire declined and underwent various military reforms.

A Roman legion typically consisted of around 5,000 to 6,000 soldiers, including both infantry and cavalry. The composition of a legion changed over time, but during the height of the Roman Empire, a legion was generally organized as follows:

Legatus Legionis: The legion commander, a senatorial appointee who was responsible for the overall command of the legion.
Tribune: Six staff officers who assisted the legion commander and were responsible for administrative duties.
Centurions: 60 to 80 officers who were responsible for the command of individual centuries (units of 80 soldiers).
Optio: An officer who served as a centurion’s second-in-command.
Decurions: Officers who commanded the cavalry units.
Auxiliaries: Non-Roman soldiers who provided support to the legion, such as archers, slingers, and light infantry.
Standard Bearers: Soldiers who carried the legion’s standards, including the eagle standard, which was a symbol of the legion’s honor and loyalty.
Legionaries: The backbone of the legion, consisting of heavy infantry soldiers who were equipped with a short sword, a rectangular shield, and a pilum (a type of javelin).
Contubernium: The smallest unit of the legion, consisting of eight legionaries who shared a tent and fought together in battle.
Support Personnel: Non-combatants such as cooks, medics, and blacksmiths who provided logistical support to the legion.

Each legion was also supported by a train of pack animals, such as mules and horses, that carried the legion’s supplies and equipment.

The Roman Empire had many legions throughout its history, and the number of legions and their names changed over time. Here are some of the most famous Roman legions:

Legio I Adiutrix
Legio I Germanica
Legio I Italica
Legio I Macriana liberatrix
Legio I Maximiana
Legio I Minervia
Legio I Parthica
Legio I Traiana Fortis
Legio II Adiutrix
Legio II Augusta
Legio II Italica
Legio II Parthica
Legio II Traiana Fortis
Legio III Augusta
Legio III Cyrenaica
Legio III Gallica
Legio III Italica
Legio IV Flavia Felix
Legio IV Macedonica
Legio IV Scythica
Legio V Alaudae
Legio VI Ferrata
Legio VI Victrix
Legio VII Claudia
Legio VII Gemina
Legio VIII Augusta
Legio IX Hispana
Legio X Fretensis
Legio XI Claudia
Legio XII Fulminata
Legio XIII Gemina
Legio XIV Gemina
Legio XV Apollinaris
Legio XVI Gallica
Legio XVII
Legio XVIII
Legio XIX
Legio XX Valeria Victrix
Legio XXI Rapax
Legio XXII Deiotariana
Legio XXIV
Legio XXX Ulpia Victrix

Note that this is not an exhaustive list, as there were many other legions throughout Roman history. The numbers of legions were also reused and reassigned over time.