The Byzantine army evolved from that of the late Roman period taking as leading models and shaping itself on the late Hellenistic armies,F. Schindler, Die Überlieferung der Strategemata des Polyainos (Vienna 1973) 187–225; E.L. Wheeler, "Notes on a Stratagem of Iphicrates in Polyaenus and Leo Tactica", Electrum 19 (2012) 157–163. but it became considerably more sophisticated in strategy, tactics and organization. The language of the army was still Latin, although later (especially after the 6th century) Greek dominated, as it became the official language of the entire empire. Unlike the Roman legions, its strength was in its cavalry, especially the armoured cataphracts, which evolved from the clibanarii of the late empire. Infantry were still used but mainly as a base of maneuver for the cavalry, as well as in specialized roles. Most of the foot-soldiers of the empire were the armoured and later on, (plural of the singular ), with the remainder being the light infantry and archers of the . The Byzantines valued intelligence and discipline in their soldiers far more than bravery or brawn. The "" () were a loyal force composed of citizens willing to fight to defend their homes and their state to the death, augmented by mercenaries. The training was very much like that of the legionaries, with the soldiers taught close combat techniques with their swords, spears and axes, along with the extensive practice of archery.A. Dain, Les manuscrits d’Onésandros (Paris 1930) 145–157; P. Rance, "The Ideal of the Roman General in Byzantium: the Reception of Onasander's Strategikos in Byzantine Military Literature", in: S. Tougher and R. Evans (eds.), Generalship in Ancient Greece, Rome and Byzantium (Edinburgh 2022) 242–263A. Dain, L’Histoire du texte d’Élien le Tacticien des origines à la Fin du Moyen Âge (Paris 1946); P. Rance, "Maurice's Strategicon and the Ancients: the Late Antique Reception of Aelian and Arrian" in P. Rance and N.V. Sekunda (edd.), Greek Taktika. Ancient Military Writing and its Heritage (Gdańsk 2017) 217–255.
Structural history
Over the course of its long history, the armies of Byzantium were reformed and reorganized many times. The only constants in its structure were its complexity and high levels of professionalism. During the 6th and 7th centuries, Hellenistic political systems, philosophies and eastern theocratic Orthodox doctrines, had forced a greater simplification in the estate administration that aimed to exercise the emperor's power in more direct means through his different viceroys in which civic and military powers would be personified in single entities with definitive powers over their respective governorships, these being the various Byzantine, Strategos, Exarchs, Doux, Katepanos among others. The main characteristics of a Theme were those of a constant source of income through the towns and villages of rural communities and large urban centers of Asia minor which allowed a simple management and great military flexibility with the ability to allow each governor general to rapidly create provincial armies when needed.
Despite having the same late Roman roots, the Byzantine army shape and reform itself on the various late Hellenistic treatises of war well known in the eastern Mediterranean, mainly Arrian and Onosander. Despite its classical bias, it was not a simple imitation of antiquity and it differed in several notable ways: It had greater numbers of heavier cavalry, archers and other missile troops, and fewer Foederati. These differences may have been contributing factors to the eastern empire's survival. It was with this Eastern Roman army that much of the western empire was reconquered in the campaigns of the generals Belisarius and Narses. It was during this time, under Justinian I, that the revitalized empire reached its greatest territorial extent and the army its greatest size of over 330,000 men by 540. Later, under the general and emperor Heraclius, the Sassanid Empire of Persia was finally defeated.
Late in Heraclius' reign, however, a major new threat suddenly arose to the empire's security in the form of the Saracens. Spurred on by their new religion, Islam, which demanded the subjugation of the world or its conversion to dar al-Islam, and driven by a still-strong tribal warfare mentality. Under the leadership of Khalid ibn al-Walid these invaders rapidly overran many of the empire's wealthiest and most important regions, especially Syria, the Levant and Egypt. This new challenge, which seriously threatened the empire's survival, compelled Heraclius and his immediate successors, in the mid-7th century, to undertake a major reform of the Byzantine military system to provide for a more cost effective local defense of its Anatolian heartland. The result was the theme system, which served as both administrative and military divisions, each under the command of a military governor or strategos.
The theme was a division-sized unit of around 9,600, stationed in the theme (administrative district) in which it was raised and named for. The themes were not simply garrison troops, however, but mobile field forces capable of supporting neighboring themes in defensive operations, or joining together to form the backbone of an imperial expeditionary force for offensive campaigns. It was under this new system that the Byzantine army is generally considered to have come into its own, distinct from its late-imperial Roman precursor. The thematic system proved to be both highly resilient and flexible, serving the empire well from the mid-7th through the late 11th centuries. Not only did it hold back the Saracens, but some of Byzantium's lost lands were recaptured. The thematic armies also vanquished many other foes including the Bulgars, Avars, Slavs and Varangians, some of whom eventually ended up in the service of Constantinople as allies or mercenaries.
In addition to the themes, there was also the central imperial army stationed in and near Constantinople called the Tagmata. The tagmata were originally battalion-sized units of guards and elite troops who protected the emperors and defended the capital. Over time, though, their size increased to that of regiments and brigades, and more of these units were formed. The term thus became synonymous with the central field army. Due to growing military pressures together with the empire's shrinking economic and manpower base, the themes began to decline. As they did so, the size and importance of the tagmata increased, due also to growing fears of the emperors over the potential dangers the and their themes posed to their power.
The final, fatal blow to the thematic army occurred in the aftermath of the disaster at the Battle of Manzikert in 1071, when a new enemy, the Seljuk Turks, overran most of Asia Minor along with most of the empire's themes. Once again, the empire was forced to adapt to a new strategic reality with reduced borders and resources. Under Emperor Alexios I Komnenos the themes were restructured around the tagmata, some of which were stationed in the provinces, but the majority usually remained near Constantinople when not on campaign. Tagmata would henceforth take on yet a third meaning as a generic term for a standing military unit of regimental size or larger.
This tagmatic army, which includes those of the Komnenian and Palaiologan dynasties, would serve the empire in its final stages from the late 11th to the mid-15th centuries, a period longer than the entire lifespans of many other empires. The tagmatic armies would also prove resilient and flexible, even surviving the near destruction of the empire in the aftermath of the fall of Constantinople to the Fourth Crusade in 1204. They would eventually retake the capital for Emperor Michael VIII Palaiologos in 1261, and though reduced by then to a small force, barely exceeding 20,000 men at most, would continue to defend the empire ably until the fall of Constantinople to the Ottoman Turks in 1453. In no small part due to increased reliance on mercenaries from the Latin west, the later tagmatic armies would come to resemble those of western Europe at the time, more than their Roman, Greek or Near-Eastern antecedents.
Infantry
Infantry types and equipment
Skoutatoi
The bulk of the Byzantine infantry were the (hoplite), named after the , a large oval, round or kite-shaped shield. Their armor and weapons were modelled following ancient Seleucid and Hellenistic infantry equipment and patterns, which included:A. Dain, Les manuscrits d’Onésandros (Paris 1930) 145–157 Helmet: the helmet varied by region and time but was generally a simple, conical-shaped piece of steel, often with extra neck protection in the form of a mail aventail or padded coif. (): a mail or scale hauberk. (): Often associated with the characteristic Byzantine lamellar cuirass, it also referred to body armor in general. In addition, pteruges (hanging leather strips) were often attached to protect the hips and thighs. (): A padded leather or textile over-garment, worn over the cuirass. () or (): A padded linen or wool under-armor, worn under the cuirass. : A heavy textile skirt hanging below a soldier's cuirass. (): a long spear (varied between in length), the kontarion was used by the first ranks of each chiliarchia (battalion) in order to form a defensive Macedonian like pike wall. (): a large oval, round (later kite-shaped) shield made of wood, covered by linen or leather and edged with rawhide, with a steel boss in earlier periods. (): The typical Roman spatha, a single handed sword (about in length, depending on the period) based on early Greek and Celtic type of swords; double-edged and weighing up to . Later it referred to the medieval arming sword, usually with a crossguard curving back towards the handle. (): a one-edged sabre-like sword, girded at the waist. Each unit had a different shield decoration often depicting earlier Hellenistic and contemporary Christian motifs. Unarmoured light infantrymen, often armed with javelins, were known as in Greek classical times as and .
Toxotai and Psiloi Like in earlier Greek states these composed the standard light infantry of the empire, in each chiliarchia they made up the last three lines. These soldiers, highly trained in the art of bow were formidable archers and highly mobile units. Most of the Imperial archers came from Asia Minor, especially the region around Trebizond on the Black sea, where they were raised, trained and equipped.
Their equipment included: Composite bow
or (small axe) for self-defence.
Although military manuals prescribed the use of light armour for archers, cost and mobility considerations would have prohibited wide-scale implementation of this.
Varangians The Varangian Guard was a foreign mercenary force and the elite of the Byzantine infantry. It was composed principally of Norsemens, Nordic, Slavic and Germanic people, after 1066 it was increasingly English in composition. The Varangians served as the bodyguard (escort) of the emperor since the time of Basil II, and were generally considered to be well-disciplined and loyal so long as funds remained to pay them. Although most of them brought their weapons with them when entering the Emperor's service, they did gradually adopt Byzantine military dress and equipment. Their most characteristic weapon was a heavy axe, hence their designation as , the "axe-bearing guard".
Infantry organization and formation