Both armies consisted of combatants from many peoples. Besides the Roman troops, the Alans, and the Visigoths,
Jordanes lists Aetius's allies as including the
Francii,
Sarmatae,
Armoriciani, Liticiani,
Burgundiones,
Saxones,
Riparii, and
Olibrones (whom he describes as "once Roman soldiers and now the flower of the allied forces"), as well as "other Celtic or German tribes." The Liticiani could be either
Laeti or
Romano-Britons, the latter of which are recorded by Gregory.
Guy Halsall argues that the Rhine
limitanei and the old British field army composed the forces of the Riparii and Armoricans, and
Peter Heather suggests that the Visigoths may have been able to field about 25,000 men total.
John F. Drinkwater adds that a faction of
Alemanni may have participated in the battle, possibly on both sides like the Franks and Burgundians. The Olibrones remain unknown, although it has been suggested these were Germanic limitanei garrisons. Schultheis argues that on paper, the Germanic federates could theoretically number more than 70,000, but likely numbered under 50,000. A sense of the size of the actual Roman army may be found in the study of the
Notitia Dignitatum by
A. H. M. Jones. This document is a list of officials and military units that was last updated in the first decades of the fifth century. The
Notitia Dignitatum lists 58 regular units, and 33
limitanei serving either in the Gallic provinces or on the frontiers nearby; the total of these units, based on Jones's analysis, is 34,000 for the regular units and 11,500 for the
limitanei, or just under 46,000 all told. This figure is an estimate for the years 395–425 and one that changes with new research. The loss of the Western Roman provinces in North Africa resulted in the loss of funding for 40,000 infantry and 20,000 cavalry in the Roman army, in addition to previous losses, which was enough to permanently cripple Roman military capacity after 439 AD. According to
Herwig Wolfram, with an annual revenue of 40,000 pounds of gold in 450 AD, the Western Empire would have had to spend almost two thirds of its income to maintain an army of 30,000 men.
Hugh Elton gives the same figure in 450, but estimates the cost of maintaining an army of 300,000 at 31,625 lbs. of gold or 7.6 solidi a year per soldier. He states that there were also other unquantifiable military costs such as defensive installations, equipment, supplies, paper, animals and other costs. The size of the army in 450 AD therefore must have been significantly reduced from its status in the late 420s. Schultheis argues that the Roman field army as calculated from his own estimates of the Notitia Dignitatum, chronology of military losses, and income losses numbered approximately 20,500
comitatenses and 18,000
limitanei by the time of the battle, not including supernumerary officers. Jordanes's list for Attila's allies includes the
Gepids under their king
Ardaric, as well as an army of various
Gothic groups led by the brothers
Valamir,
Theodemir (the father of the later Ostrogothic king
Theodoric the Great) and
Videmir, scions of the
Amali Goths.
E. A. Thompson expresses his suspicions that some of these names are drawn from literary traditions rather than from the event, On the other hand, Thompson believes that the presence of Burgundians on the Hunnic side is credible, noting that a group is documented remaining east of the Rhine; he believes that the other peoples Sidonius mentions (the
Rugians, Sciri, and
Thuringians) were participants in this battle. Although there is no direct evidence that Heruli were present, as indirect evidence, centuries later
Paulus Diaconus listed the subject peoples Attila could call upon in addition to the better known Goths and Gepids: "Marcomanni, Suebi, Quadi, and alongside them the Herules, Thuringi and Rugii". Thompson remarks in a footnote, "I doubt that Attila could have fed an army of even 30,000 men". Lindner argues that by crossing the
Carpathians to the area of modern
Hungary the Huns had forfeited their best logistic base and grazing grounds, and that the
Great Hungarian Plain could only support 15,000 mounted nomads. Schultheis notes that Attila had control of other Hunnic groups east of the Carpathians, and proposes the eastern half of Attila's empire could field an additional 7,000 to 12,000 men based on later 6th century sources. Kim notes that the Huns continued to use the Xiongnu decimal system, meaning their army was probably organised into divisions of 10, 100, 1000, and 10,000, but no real estimates of Hunnic military capacity can be determined. Their barbarian allies do receive mentions at other times in other sources: in 430 CE. The Hunnish king
Octar was defeated by a force of 3,000
Neckar Burgundians who would later come under Hun subjugation, and Heather estimates that the
Gepids and the
Amali Goths could have each fielded a maximum of 15,000 men at the
Battle of Nedao in 454. Schultheis argues that when combining primary and secondary source estimates Attila's forces would number more than 100,000 on paper, but were likely closer to 70,000. The Chronicon Paschale, which preserves an extremely abbreviated and garbled fragment of Priscus's account of the campaign, states that Attila's forces numbered in the tens of thousands. Assuming that the Hunnic and Germanic forces were roughly the same size as the Roman and federate army, those involved in the battle could have been well in excess of 100,000 combatants in total. This excludes the inevitable servants and camp followers who usually escape mention in the primary sources. ==Site of the Catalaunian Plains==