Agricola’s Forces

Agricola’s Legions

From the time of Augustus, the Roman Army maintained a foundation of 28 legions, strategically positioned across the empire for potential expansions. A legion typically consisted of about 5,000 Roman citizens, primarily serving as heavy infantry. The fundamental unit within a legion was the cohort, further divided into six centuries, each led by a centurion. Beyond combat, legions were multifaceted units, encompassing specialist technicians, craftsmen, medics, and administrators. Soldiers were often assigned various tasks related to administration or construction on behalf of the imperial government. During Agricola’s tenure as governor, Britain hosted four legions: Legio II Augusta, Legio II Adiutrix, Legio IX Hispana, and Legio XX Valeria Victrix.

Agricola’s Auxiliary Troops

Alongside the core legions, Roman emperors also recruited smaller units of troops from among Rome’s allied and tributary nations, particularly from groups known for their martial prowess like the Gauls, Germans, and Spaniards. These men didn’t meet the citizenship requirement for legionary service, so they were formed into separate units called auxilia, which means ‘assistance.’ Upon completing 25 years of service, these veterans were granted citizenship, often documented by a bronze diploma – two bronze sheets bound together to legally certify their new status.

Despite being viewed by some, including Tacitus, as ‘pillagers of the world’, the auxilia contributed significantly to the intimidating image of Rome’s disciplined standing army. These auxiliary units varied, with some being purely infantry, divided into centuries and organized into independent cohorts. Generally, their status was considered inferior to the legionaries. An auxiliary infantryman, for instance, typically earned only 5/6th of a legionary’s pay, and their equipment was often perceived as not matching the high standard of the legionaries. Additionally, auxiliaries commonly shouldered the bulk of garrison duties, freeing up legionaries for construction work. Yet, each played a distinct and vital role in battle, with auxiliaries being integral to the Roman military establishment.

The Roman army primarily comprised infantry, so specialized auxiliary units were essential for providing cavalry support. These included alae (literally ‘wings’), which were entirely cavalry squadrons divided into 16 troops (turmae), each led by a decurion. More common than the alae were the cohortes equitatae (‘equitate cohorts’), consisting of both infantry and cavalry in a rough ratio of four to one, offering greater operational flexibility than pure infantry units.

Auxiliary Ala

In terms of privileges and pay, cavalrymen generally fared better than infantry. For instance, a cohortal trooper (eques cohortis) was paid a salary comparable to a legionary. However, an auxiliary cavalryman (eques alaris) earned 7/6th of a legionary’s salary, while auxiliary infantrymen received considerably less.

Agricola’s cavalry likely included several units like Ala Primae Hispanorum Asturum, Ala Primae Thracum, and Ala Primae Tungrorum, among others. While the Ala Augusta Sebosiana is directly attested during this period, the presence of other regiments like Ala Augusta Gallorum Petriana is inferred from various sources, including tombstones and military diplomas issued to veterans by Emperor Trajan in AD 98, 103, and 105. These diplomas suggest these units might have been in Britain under Agricola, especially as troop withdrawals were more common than new arrivals in the AD 80s and 90s. However, the diplomas do not cover all units in the provincial army. For instance, Ala Augusta Sebosiana, which had troopers buried at Lancaster (Calunium) during the Flavian period, and Ala Secundae Asturum, which appears in Britain under Hadrian but was earlier in Pannonia, might have arrived with different commanders or at different times, indicating gaps in the historical record.

Various cavalry units in the Roman army were recognized for their commendable service. For instance, the Ala Hispanorum Vettonum, initially recruited from the Vettones in central Spain, was awarded Roman citizenship, likely for bravery during the early stages of the invasion. This is hinted at by the trooper Lucius Vitellius Tancinus commemorated at Bath, who adopted his Roman name from L. Vitellius, a contemporary of Emperor Claudius.

Similarly, the Ala Augusta Gallorum Petriana received citizenship before their deployment to Britain, possibly accompanying Quintus Petillius Cerialis in AD 71, along with Ala Augusta Sebosiana.

Ala Classiana, probably raised in Gaul and later known as Ala Gallorum et Thracum Classiana, also received citizenship, reflecting its Gallic roots and Thracian reinforcements. These three units were henceforth known as ala civium Romanorum (‘squadron of Roman citizens’). Additionally, ala Classiana earned the titles invicta bis torquata (‘invincible, twice decorated’), though the exact reasons for these honours are unknown.

Infantry Cohorts

Infantry outnumbered cavalry in Agricola’s army. The early Trajanic diplomas provide insights into the composition of his forces, though caution is advised as some units, like Cohors Primae Alpinorum and possibly Cohors Secundae Thracum, had only recently been transferred to the province. The possibility of units with similar names, especially from prolific recruiting areas like Thrace and the Iberian peninsula, adds complexity to understanding the army’s makeup.

Another factor affecting the size of Agricola’s army is the emerging trend of double-strength cohorts during the Flavian period. Additionally, some units might have been overlooked in historical records. For instance, while Cohors Quartae Delmatarum is mentioned in the diplomas, the early history of Cohors Primae Delmatarum and Cohors Secundae Delmatarum Equitata, which later appear in Britain, remains unknown, unlike Cohors Tertiae Delmatarum, known to have been based in Germany.

Agricola’s army is speculated to have included these cohorts:

While definitive evidence for the presence of these units in Britain during this time is scarce, several sources provide strong circumstantial evidence. For instance, Cohors Primae Hispanorum equitata buried a soldier at Ardoch (Alavna Veniconvm) around this time, and Cohors Secundae Asturum equitata is likely to have played a significant role in the battle at Mons Graupius.

Tacitus mentions the presence of two Tungrian cohorts and four Batavian cohorts in Agricola’s army. Cohors Primae Batavorum Equitata and II Batavorum, first recorded in Pannonia in AD 98, were likely in Britain earlier, along with Cohors Tertiae Batavorum Antoniniana milliaria equitata and Cohors Nona Batavorum, both of which left records at Vindolanda. Cohors Primae Ubiorum, despite a mutiny during its initial training, was also part of the army.

Many of these cohorts likely arrived with Govenor Quintus Petilius Cerialis (AD71 -73/4) in AD 71. Cohors Primae Vardullorum’s unique epithet “fida” might have been earned on the Rhine during the AD 69 events. Units like Cohors Primae Baetasiorum civium Romanorum, Cohors Primae Cugernorum, Cohors Primae Frisiavonum, and Cohors Primae Fida Vardullorum, all from the Rhineland, as well as Cohors Primae Morinorum and the Cohors Primae Lingonum, were possibly new recruits post-AD 69.

Professor Richmond, in his work on the Agricola, highlighted the British auxiliaries mentioned by Tacitus, suggesting they were newly recruited units from southern England. However, it’s more likely that Tacitus referred to Britons recruited into existing regiments. Richmond’s list includes ala Brittonum (veterana) and ala I Flavia Augusta Britannica, but these are less likely to have been part of Agricola’s army. The former is not known before the 2nd century AD and was stationed in Lower Pannonia, indicating a Trajanic origin. The latter’s title “Britannica” suggests prior service in Britain, possibly during the initial invasion.

Among the cohorts listed by Richmond, cohors I Brittonum appears the most plausible for having served under Agricola, as evidenced by its appearance on an AD 85 diploma (CIL 16, 31). The veterans discharged that year would have been recruited around AD 60. However, this diploma relates to the Pannonian army, with no indication that cohors I Brittonum ever served in Britain. Similarly, time-served veterans from cohors II Brittonum, discharged in Lower Moesia in AD 99 (CIL 16, 45), and cohors III Brittonum, released in Upper Moesia in AD 100 (CIL 16, 46), were likely recruited around AD 75, but again, there’s no evidence of their service in Britain.

Estimates that Agricola commanded 80 or 90 auxiliary regiments are probably exaggerated. During Hadrian’s reign, when Britain had one of the empire’s larger garrisons, there were only about a dozen alae and 30-odd cohorts. Therefore, it’s unlikely that Agricola’s army exceeded this number. While certainty is elusive without more epigraphic evidence, the nine or ten alae and 24 cohorts previously listed likely constituted the majority of Agricola’s forces. Future epigraphic discoveries may provide further insights into the exact composition of Agricola’s army.