Byzantine army

From the 6th to the 12th centuries, the Byzantine army was among the most powerful and effective military forces in the world – neither Middle Ages Europe nor (following its early successes) the fracturing Caliphate could match the strategies and the efficiency of the Byzantine army. Restricted to a largely defensive role in the 7th to mid-9th centuries, the Byzantines developed the theme system to counter the more powerful Caliphate. From the mid-9th century, however, they gradually went on the offensive, culminating in the great conquests of the 10th century under a series of soldier-emperors such as Nikephoros II Phokas, John Tzimiskes and Basil II. The army they led was less reliant on the militia of the themes; it was by now a largely professional force, with a strong and well-drilled infantry at its core and augmented by a revived heavy cavalry arm. With one of the most powerful economies in the world at the time, the Empire had the resources to put to the field a powerful host when needed, in order to reclaim its long-lost territories.

After the collapse of the theme system in the 11th century, the Byzantines grew increasingly reliant on professional Tagmata troops, including ever-increasing numbers of foreign mercenaries. The Komnenian emperors made great efforts to re-establish a native army, instituting the pronoia system of land grants in exchange for military service. Nevertheless, mercenaries remained a staple feature of late Byzantine armies since the loss of Asia Minor reduced the Empire's recruiting-ground, while the abuse of the pronoia grants led to a progressive feudalism in the Empire. The Komnenian successes were undone by the subsequent Angeloi dynasty, leading to the dissolution of the Empire at the hands of the Fourth Crusade in 1204.

The Emperors of Nicaea managed to form a small but effective force using the same structure of light and heavily armed troops, both natives and foreigners. It proved effective in defending what remained of Byzantine Anatolia and reclaiming much of the Balkans and even Constantinople itself in 1261. Another period of neglect of the military followed in the reign of Andronikos II Palaiologos, which allowed Anatolia to fall prey to an emerging power, the Ottoman Empire. Successive civil wars in the 14th century further sapped the Empire's strength and destroyed any remaining chance of recovery, while the weakening of central authority and the devolution of power to provincial leaders meant that the Byzantine army was now composed of a collection of militias, personal entourages and mercenary detachments.

History

In the period after the Muslim conquests, which saw the loss of Syria and Egypt, the remnants of the provincial armies were withdrawn and settled in Asia Minor, initiating the thematic system. Despite this unprecedented disaster, the internal structures of the army remained much the same, and there is a remarkable continuity in tactics and doctrine between the 6th and 11th centuries. The Battle of Manzikert in 1071 and the subsequent Seljuk invasions, together with the arrival of the Crusades and the incursions of the Normans, would severely weaken the Byzantine state and its military, which increasingly had to rely on foreign mercenaries.

The army under Diocletian and Constantine

The Eastern Empire dates from the creation of the Tetrarchy ("Quadrumvirate") by the Emperor Diocletian in 293. His plans for succession did not outlive his lifetime, but his reorganization of the army did by centuries. Rather than maintain the traditional infantry-heavy legions, Diocletian reformed it into limitanei ("border") and comitatenses (field armies). However, the last legion, Legio V Macedonica, survived until 637, when it was destroyed during the Arab invasion of Egypt.

There was an expansion of the importance of the cavalry, though the infantry still remained the major component of the Roman armies, in contrast to common belief. In preparation for Justinian's African campaign of 533–534 AD, the army assembled amounted to 10,000-foot soldiers and 5,000 mounted archers and federate lancers.

The limitanei and ripenses were to occupy the limes, the Roman border fortifications. The field units, by contrast, were to stay well behind the border and move quickly where they were needed, whether for offensive or defensive roles, as well as forming an army against usurpers. The field units were held to high standards and took precedence over Limitanei in pay and provisions.

Cavalry formed about one-third of the units, but as a result of smaller units, about one-quarter of the Roman armies consisted of cavalry. About half the cavalry consisted of heavy cavalry (including the stablesiani). They were armed with spear or lance and sword and armored in mail. Some had bows, but they were meant for supporting the charge instead of independent skirmishing.

In the field armies there was a component of some 15% of cataphractarii or clibanarii, heavily armoured cavalry who used shock tactics. The light cavalry (including the scutarii and promoti) featured high amongst the limitanei, being very useful troops on patrol. They included horse archers (Equites Sagittarii). The infantry of the comitatenses was organized in regiments (variously named legiones, auxilia or just numeri) of about 500–1,200 men. They were still the heavy infantry of old, with a spear or sword, shield, body armour and a helmet. But now each regiment was supported by a detachment of light infantry skirmishers.

If needed, the infantry could take off (some of) their armour to act in a more flexible way as Modares did (according to Zosimus) during the Gothic War of the 370s. The regiments were commanded by a tribunus ("tribune") and brigaded in pairs (cavalry units did, too) under a comes. These brigades probably were tactical and strategic units only, as no traces survive of brigade staff corps.

On the other hand, little is known of the limitanei. The old legions, cohorts and cavalry alae survived there, and newer units were created (the new legions, or auxilia and vexillationes), amongst the cavalry. The limitanei infantry may have been lighter-equipped than the comitatenses infantry, but there is no evidence whatsoever. They were paid less than the field troops and recruited locally. Consequently, they were of inferior quality. However, they were in the line of fire. They countered most incursions and raids. Thus, it can be assumed they had superior field experience (except in periods of long campaigning for the comitatenses), though that experience did not extend to large battles and sieges.

The Scholae Palatinae units, which were more properly known as the Schola Protectores Domestici and the "Protective Association of the Royal Escort" (also called the Obsequium), were the personal guard of the Emperor, and were created to replace the Praetorian Guard disbanded by Constantine I.

Following a major reorganisation of the Roman army during the Emperor Diocletian's reign (284–305 AD) the legions in the third and fourth century bore little resemblance to those of the Republic or earlier Roman empire. Reduced in numbers to about 1,000 men per legion, these units became static garrison troops, sometimes serving on a part-time militia basis as hereditary limitanei. As such they were separate from the new mobile field army.

The army of Justinian I and his successors

The army of Justinian I was the result of fifth-century reorganizations to meet growing threats to the empire, the most serious from the expanding Persian empire. Gone were the familiar legions, cohorts and alae of old Rome, and in their place were small Greek infantry battalions or horse regiments called an arithmos, tagma or numerus. A numerus had between 300 and 400 men and was commanded by a Stratarches. Two or more numeri formed a brigade, or moira; two or more brigades a division, or meros.

There were six classifications of troops:

1. The guard troops stationed in the capital.
2. The comitatenses of the old Roman field armies. In Justinian's day these were more commonly called stratiotai. Regular soldiers of the early Byzantine army, the stratiotai were chiefly recruited from subjects of the empire in the highlands of Thrace, Illyricum and Isauria.
3. The limitanei. The least changed element of the Roman army, limitanei still performed their traditional duties of guarding frontiers and garrisoning border posts. Like how the comitatenses were called stratiotai in the heyday of the Justinians, the limitanei were known as akritai by the mainly Greek-speaking subjects of the Eastern Empire. This terming of limitanei as akritai in Greek, led to folktales of the heroism of the limitanei/akritai, especially the popular tale of the hero Digenes Akritas during the wars between the Byzantines and the various Arab Caliphates.
4. The foederati. They were a relatively new element in the army, recruited from the fifth century onwards from barbarian volunteers. They were formed into cavalry units under Byzantine "Gothic" officers. A ban on enlistments by Byzantine subjects was lifted in the sixth century, and their composition became mixed.
5. The Allies. These were bands of barbarians, Huns, Herules, Goths or others who were bound by treaty to provide the empire with military units commanded by their own chiefs, in return for land or yearly subsidy.
6. The bucellarii. The private armed retainers of generals, Praetorian Prefects, officers of lesser rank and the rich, the bucellarii were often a significant portion of a field army's cavalry force. The size of a retinue of bucellarii depended on the wealth of the employer. Their rank and file were called hypaspistai, or shield-bearers, and their officers, doryphoroi or spear-bearers. Doryphoroi took solemn oaths of fidelity to their patron and of loyalty to the emperor. One of the most noted generals of the period, Belisarius, had been a doryphoros in Justinian's retinue before his becoming emperor. The bucellarii were usually mounted troops, mostly Huns, Goths and mountaineers of Thrace or Asia Minor.

The size of Justinian's army is unclear. Bury, writing in the 1920s, accepted the estimate of 150,000 troops of all classes in 559 given by Agathia of Myrina in his History. Norwich also estimated the army under Justinian at 150,000 soldiers. Other scholars estimate the total strength of the imperial army under Justinian to be between 300,000 and 350,000 soldiers. Field armies generally had 15,000 to 25,000 soldiers and were formed mainly of comitatenses and foederati, reinforced by the commanders' retinues and barbarian allies. The expeditionary force of Belisarius during his reconquest of Carthage from the Vandals in 533 is illustrative.

This army had 10,000 comitatenses and foederati infantry, with 3,000 similarly composed cavalry. There were 600 Huns and 400 Herules, all mounted archers, and 1,400 or 1,500 mounted bucellarii of Belisarius' retinue. The small force of less than 16,000 men voyaged from the Bospherus to North Africa on 500 ships protected by 92 dromons, or war-ships.

Tactics, organization and equipment had been largely modified to deal with the Persians. The Byzantines adopted elaborate defensive armor from Persia, coats of mail, cuirasses, casques and greaves of steel for tagma of elite heavy cavalrymen called cataphracts, who were armed with bow and arrows as well as sword and lance.

Large numbers of light infantry were equipped with the bow, to support the heavy infantry known as scutatii (Meaning ″shield men″) or skutatoi. These wore a steel helmet and a coat of mail, and carried a spear, axe and dagger. They generally held the centre of a Greek line of battle. Infantry armed with javelins were used for operations in mountain regions.

Notable military events during the reign of Justinian included the battle of Dara in 530, when Belisarius, with a force of 25,000, defeated the Persian emperor's army of 40,000. In addition to his reconquest of Carthage, noted above, Belisarius also recaptured Sicily, Naples, Rome and the rest of Italy from the Goths in a war lasting from 535 to 554. Another famous commander of the time was the imperial eunuch Narses, who defeated a Gothic army at Busta Gallorum on the eastern coast of Italy in 552.

Towards the end of the sixth century, the Emperor Maurice, or senior officers writing for him, described in great detail the Byzantine army of the period in The Strategikon, a manual for commanders. Maurice, who reigned from 582 to 602, certainly had extensive military experience. In 592, he forced the Persians to sign a treaty that regained extensive Armenian territory for the empire that had been lost in earlier wars. Maurice then turned to the western frontier in the Balkans. In a war that lasted the rest of his life, he defeated the Avars and Slavs in battle, but could not gain a decisive victory.

The Strategikon's author gives us a fair picture of the Byzantine army and its troops, including the equipment borrowed from the Herules, Goths, Slavs and especially the Avars, once barbarian enemies all. Cavalrymen should have "hooded coats of mail reaching to their ankles which may be drawn up by thongs and rings, along with carying cases." Helmets were to have small plumes on top and bows were to be suited to the strength of each man, their cases broad enough that strung bows can fit in them, and spare bow strings kept the men's saddle bags. The men's quivers should have covers and hold 30 or 40 arrows and they should carry small files and awls in their baldrics. The cavalry lances should be "of the Avar type with leather thongs in the middle of the shaft and with pennons." The men were also to have "swords and round neck pieces of the Avar type with linen fringes outside and wool inside." Young foreigners unskilled with the bow should have lances and shields and bucellary troops ought to have iron gauntlets and small tassles hanging from the back straps and neck straps of their horses, as well as small pennons hanging from their own shoulders over their coats of mail, "for the more handsome the soldier is, in his armament, the more confidence he gains in himself and the more fear he inspires in the enemy." Lances were apparently expected to be thrown, for the troops should have "two lances so as to have a spare in case the first one misses. Unskilled men should use lighter bows."

The manual then describes horse gear and the trooper's clothing. "The horses, especially those of the officers and the other special troops, in particular those in the front ranks of the battle line, should have protective pieces of iron armor about their heads and breast plates of iron or felt, or else breast and neck coverings such as the Avars use. The saddles should have large and thick cloths; the bridles should be of good quality; attached to the saddles should be two iron stirrups, a lasso with thong, hobble, a sadle bag large enough to hold three or four days' rations when needed. There should be four tassels on the back strap, one on top of the head, and one under the chin."

"The men's clothing," the Strategikon continues, "especially their tunics, whether made of linen, goat's hair or rough wool, should be broad and full, cut according to the Avar pattern, so they can be fastened to cover the knees while riding and give a neat appearance. They should also be provided with an extra-large cloak or hooded mantle of felt with broad sleeves to wear, large enough to wear over their armament, including the coat of mail and the bow." "Each squad should have a tent, as well as sickles and axes to meet any contingency. It is well to have tents of the Avar type, which combine practicality with good appearance."

"The men," according to The Strategikon, "should certainly be required to provide servants for themselves, slave or free ... Should they neglect this and find themselves without servants, then in time of battle it will be necessary to detail some of the soldiers themselves to the baggage train, and there will be fewer men fighting in the ranks. But if, as can easily happen, some of the men are unable to afford servants, then it will be necessary to require that three or four soldiers join in maintaining one servant. A similar arrangement should be made with the pack animals, which may be needed to carry the coats of mail and the tents."

The manual then describes a system of unit identification that sounds like a fore-runner of medieval heraldry. The flags of a meros or division, should be the same color. The streamers of its immediate sub-units, the several moiras or brigades, should also have their own color. Thus, the manual states, "each individual tagma, (battalion or squadron) may easily recognize its own standard. Other distinctive devices known to the soldiers should be imposed on the fields of the flags, so that they may easily be recognized according to meros, moira and tagma. The standards of the merarchs (meros commander) should be particularly distinctive and conspicuous, so they may be recognized by their troops at a great distance."

The Strategikon deals more briefly with the infantry. They are to wear Gothic tunics "coming down to their knees or short ones split up the sides and Gothic shoes with thick soles, broad toes and plain stitching, fastened with no more than two clasps the soles studded with a few nails for greater durability." Boots or greaves are discouraged, "for they are unsuitable for marching and, if worn, slow one down. Their mantles should be simple, not like Bulgarian cloaks. Their hair should be cut short, and it is better if it is not allowed to grow long."

The descriptions of the armament of the "heavy-armed infantrymen" are equally terse. "The men of each arithmos or tagma," the Strategikon tells us, "should have shields of the same color, Herulian swords, lances, helmets with small plumes and tassels on top and on the cheek plates – at least the first men in the file should have these – slings, and lead-pointed darts. The picked men of the files should have mail coats, all of them if it can be done, but in any case the first two in the file. They should also have iron or wooden greaves, at least the first and second in each file."

The light-armed infantryman, still quoting the Strategikon, "should carry bows on their shoulders with large quivers holding about 30 or 40 arrows. They should have small shields, as well as crossbows with short arrows in small quivers. These can be fired a great distance with the bows and cause harm to the enemy. For men who might not have bows or are not experienced archers, small javelins or Slavic spears should be provided. They should also carry lead-pointed darts in leather cases, and slings."

The strength of the Byzantine army and navy in 565 is estimated by Treadgold to have been 379,300 men, with a field army and part of the guards totaling 150,300, and the frontier troops, part of the guards and the oarsmen totaling 229,000. These numbers probably held through the reign of Maurice. However, the largest field army mentioned in the Strategikon is a force of 34,384 (16,384 heavy infantry, 8,000 light-armed troops and 10,000 cavalry) which is given as an example of "the past, when the legions were composed of large numbers of men." Writing of his own time, Maurice stipulates that an army of more than 24,000 men should be divided into four components and an army of less than 24,000 into three. In another section, Maurice describes the formation of cavalry tagmas of 300 to 400 men into morias of 2,000 to 3,000 and the morias into meros of 6,000 to 7,000.

Middle Byzantine period, 7th–11th centuries

The Themata

The themata (Gr. θέματα) were administrative divisions of the empire in which a general (Gr. στρατηγός, strategos) exercised both civilian and military jurisdiction and a Judge (Κριτής του Θέματος, Krites tou thematos) held the judicial power. The name is peculiar; Treadgold's closest guess is that thema was being used to denote "emplacements". Modern historians agree that the designations of the first themes came from the field armies that were stationed in Asia Minor.

The themata were organized as a response to the enormous military and territorial losses suffered during the conquests of the Muslim Rashidun Caliphate – Syria in 637, Armenia and Egypt in 639, North Africa in 652 and Cyprus in 654. Treadgold cites estimates that indicate the empire's population dropped from 19.5 million in 560 to 10.5 million in 641. At the same time the size of armed forces plunged from 379,300 men to 129,000.

By 662, the empire had lost more than half its territory in 30 years, and the first mentions occur in surviving records of themata under the command of generals, or strategi, that are the remnants of the former mobile armies now stationed in set districts. At some later time, when payment in cash had become difficult, the soldiers were given land grants within their districts for their support.

The dates of this process are uncertain, but Treadgold points to 659–662 as the most likely time-frame, as this is the period when the Emperor Constans II made a truce with the Arabs that gave the army time to regroup, the government ran out of money to pay the troops, and the empire's enormous losses of territory stopped. The themata provided a bulwark against Arab invasions and raids that lasted until the late 11th century. Themata were also formed in the west, as a response to the Serb and Bulgar incursions that drove the empire's frontier from the Danube River south to Thrace and the Peloponnese.

The five original themata were all in Asia Minor and originated from the earlier mobile field armies. They were:

• the Armeniac Theme (Θέμα Άρμενιάκων, Thema Armeniakōn), first mentioned in 667, was the successor of the Army of Armenia. It occupied the old areas of the Pontus, Armenia Minor and northern Cappadocia, with its capital at Amasea
• the Anatolic Theme (Θέμα Άνατολικῶν, Thema Anatolikōn), first mentioned in 669, was the successor of the Army of the East (Άνατολῆ). It covered central Asia Minor, and its capital was Amorium.
• the Opsician Theme (Θέμα Ὀψικίου, Thema Opsikiou), first mentioned in 680, was where the imperial retinue (in Latin Obsequium), was established. It covered northwestern Asia Minor (Bithynia, Paphlagonia and parts of Galatia), and was based at Nicaea. Its commander bore the title of komēs ("count")
• the Thracesian Theme (Θέμα Θρακησίων, Thema Thrakēsiōn), first mentioned in 680, was the successor of the Army of Thrace. It covered the central western coast of Asia Minor (Ionia, Lydia and Caria), with capital at Ephesos.
• the corps of the Carabisiani (Kαραβησιάνοι, Karabēsianoi), first mentioned in 680, probably formed from the remnants of the Army of the Illyricum or the old quaestura exercitus. It occupied the southern coast of Asia Minor and the Aegean Islands, with its capital at Attaleia. It was a naval corps (κάραβις means "ship"), and its commander bore the title of droungarios. It was replaced with the Cibyrrhaeot Theme in the early 8th century.

Within each theme, eligible men were given grants of land to support their families and to equip themselves. Following revolts strengthened by the large size of these divisions, Leo III the Isaurian, Theophilus, and Leo VI the Wise all responded by breaking the themes up into smaller areas and dividing control over the armies within each theme into various tourmai. The large early themes were progressively split up in the 8th–9th centuries to reduce their governors' power, while in the 10th century, new and much smaller themes, called "Armenian themes" because many were settled by Armenians, were created in the East in conquered territories. While in ca. 842 the Taktikon Uspensky lists 18 strategoi of themes, the De Thematibus of ca. 940 lists 28, and the Escorial Taktikon, written ca. 971–975, lists almost 90 strategoi of themes and other military commands.

Sicily had been completely lost to the expanding Emirate of Sicily at the beginning of Constantine VII's reign in 905 and Cyprus was a condominium jointly administered with the Abbasid Caliphate until its reconquest by Nikephoros II Phokas in 965. Constantinople itself was under an Eparch and protected by the numerous tagmata and police forces.

The empire is estimated by Treadgold to have had a population of 7 million in 774, with an army and navy that totaled 118,400. This included 62,000 thematic troops in 10 themes (including 4,000 marines in the naval themes of Hellas and Cibyrrhaeot), 18,000 in six tagmas, and 38,400 oarsmen divided between the Imperial fleet and the naval themes. By 840, the population had grown by a million, while the army had expanded to a total strength of 154,600. There were 96,000 soldiers and marines in 20 themes and 24,000 in the tagmas, while the number of Imperial and thematic oarsmen declined to 34,200.

Under the direction of the thematic strategoi, tourmarchai commanded from two up to four divisions of soldiers and territory, called tourmai. Under them, the droungarioi headed subdivisions called droungoi, each with a thousand soldiers. In the field, these units would be further divided into banda with a nominal strength of 300 men, although at times reduced to little more than 50. Again, the fear of empowering effective revolts was largely behind these subdivisions.

The following table illustrates the thematic structure as found in the Thracesian Theme, circa 902–936.

The Imperial tagmata

The tagmata (τάγματα, "regiments") were the professional standing army of the Empire, formed by Emperor Constantine V after the suppression of a major revolt in the Opsician Theme in 741–743. Anxious to safeguard his throne from the frequent revolts of the thematic armies, Constantine reformed the old guard units of Constantinople into the new tagmata regiments, which were meant to provide the emperor with a core of professional and loyal troops. They were typically headquartered in or around Constantinople, although during the 10th century they sent detachments to the provinces. The tagmata were a mixture of heavy cavalry and heavy infantry units and formed the core of the imperial army on campaign, augmented by the provincial levies of thematic troops who were more concerned with local defense.

The four main tagmata were:

• the Scholai (Gr. Σχολαί, "the Schools"), the most senior unit, the direct successor of the imperial guards established by Constantine the Great.
• the Exkoubitoi or Exkoubitores (Lat. Excubiti, Gr. Ἐξκούβιτοι, "the Sentinels"), established by Leo I.
• the Arithmos (Gr. Ἀριθμός, "Number") or Vigla (Gr. Βίγλα, from the Latin word for "Watch"), promoted from thematic troops by the Empress Eirene in the 780s, but of far older ancestry, as the archaic names of its ranks indicate. By the reign of Nicephorus I (802–11) the Vigla had become a permanent part of the tagmata with responsibility for guarding the Sacred Palace and the Hippodrome in Constantinople. The regiment performed special duties on campaign, including guarding the imperial camp, relaying the Emperor's orders, and guarding prisoners of war.
• the Hikanatoi (Gr. Ἱκανάτοι, "the Able Ones"), established by Emperor Nicephorus I in 810.

There were also auxiliary tagmata, such as the Noumeroi (Gr. Νούμεροι), a garrison unit for Constantinople, which probably included the regiment "of the Walls" (Gr. τῶν Τειχέων, tōn Teicheōn), manning the Walls of Constantinople, and the Optimatoi (Gr. Ὀπτιμάτοι, "the Best"), a support unit responsible for the mules of the army's baggage train (the τοῦλδον, touldon).

Treadgold estimates that between 773 and 899, the strength of the Schools, Excubitors, Watch and Hicanati was 16,000 cavalrymen, that of the Numera and Walls 4,000 infantry. The Optimates had 2,000 support troops until sometime after 840, when their strength was raised to 4,000. In circa 870, the Imperial Fleet Marines were founded, adding another 4,000, for a total active force of 28,000.

There was also the Hetaireia (Gr. Ἑταιρεία, "Companions"), which comprised the various mercenary corps in Imperial service, subdivided in Greater, Middle and Lesser, each commanded by a Hetaireiarchēs recalling the royal Macedonian company of old.

In addition to these more or less stable units, any number of shorter-lived tagmata were formed as favoured units of various emperors. Michael II raised the Tessarakontarioi, a special marine unit, and John I Tzimiskes created a corps called the Athanatoi (Gr. Ἀθάνατοι, the "Immortals") after the old Persian unit.

The army during the Komnenian dynasty

Establishment and successes

At the beginning of the Komnenian period in 1081, the Byzantine Empire had been reduced to the smallest territorial extent in its history. Surrounded by enemies, and financially ruined by a long period of civil war, the empire's prospects had looked grim. Yet, through a combination of skill, determination and years of campaigning, Alexios I Komnenos, John II Komnenos and Manuel I Komnenos managed to restore the power of the Byzantine Empire by constructing a new army from the ground up.

The new force is known as the Komnenian army. It was both professional and disciplined. It contained formidable guards units such as the Varangian Guard and the Immortals (a unit of heavy cavalry) stationed in Constantinople, and also levies from the provinces. These levies included cataphract cavalry from Macedonia, Thessaly and Thrace, and various other provincial forces from regions such as the Black Sea coast of Asia Minor.

Under John II, a Macedonian division was maintained, and new native Byzantine troops were recruited from the provinces. As Byzantine Asia Minor began to prosper under John and Manuel, more soldiers were raised from the Asiatic provinces of Neokastra, Paphlagonia and even Seleucia (in the south east). Soldiers were also drawn from defeated peoples, such as the Pechenegs (cavalry archers), and the Serbs, who were used as settlers stationed at Nicomedia.

Native troops were organised into regular units and stationed in both the Asian and European provinces. Komnenian armies were also often reinforced by allied contingents from the Principality of Antioch, Serbia and Hungary, yet even so they generally consisted of about two-thirds Byzantine troops to one-third foreigners. Units of archers, infantry and cavalry were grouped together so as to provide combined arms support to each other.

This Komnenian army was a highly effective, well-trained and well-equipped force, capable of campaigning in Egypt, Hungary, Italy and Palestine. However, like many aspects of the Byzantine state under the Komnenoi, its biggest weakness was that it relied on a powerful and competent ruler to direct and maintain its operations. While Alexios, John and Manuel ruled (c. 1081–c. 1180), the Komnenian army provided the empire with a period of security that enabled Byzantine civilization to flourish. Yet, at the end of the twelfth century the competent leadership upon which the effectiveness of the Komnenian army depended largely disappeared. The consequences of this breakdown in command were to prove disastrous for the Byzantine Empire.

Neglect under the Angeloi

In the year 1185, the emperor Andronikos I Komnenos was killed. With him died the Komnenos dynasty, which had provided a series of militarily competent emperors for over a century. They were replaced by the Angeloi, who have the reputation of being the most unsuccessful dynasty ever to occupy the Byzantine throne.

The army of the Byzantine empire at this point was highly centralised. It was dominated by a system in which the emperor gathered together his forces and personally led them against hostile armies and strongholds. Generals were closely controlled, and all arms of the state looked to Constantinople for instruction and reward.

However, the inaction and ineptitude of the Angeloi quickly lead to a collapse in Byzantine military power, both at sea and on land. Surrounded by a crowd of slaves, mistresses and flatterers, they permitted the empire to be administered by unworthy favourites, while they squandered the money wrung from the provinces on costly buildings and expensive gifts to the churches of the metropolis. They scattered money so lavishly as to empty the treasury, and allowed such licence to the officers of the army as to leave the Empire practically defenceless. Together, they consummated the financial ruin of the state.

The empire's enemies lost no time in taking advantage of this new situation. In the east the Turks invaded the empire, gradually eroding Byzantine control in Asia Minor. Meanwhile, in the west, the Serbs and Hungarians broke away from the empire for good, and in Bulgaria the oppressiveness of Angeloi taxation resulted in the Vlach-Bulgarian Rebellion late in 1185. The rebellion led to the establishment of the Second Bulgarian Empire on territory which had been vital to the empire's security in the Balkans.

Kaloyan of Bulgaria annexed several important cities, while the Angeloi squandered the public treasure on palaces and gardens and attempted to deal with the crisis through diplomatic means. Byzantine authority was severely weakened, and the growing power vacuum at the centre of the empire encouraged fragmentation, as the provinces began to look to local strongmen rather than the government in Constantinople for protection. This further reduced the resources available to the empire and its military system, as large regions passed outside central control.

Analysis of the Byzantine military collapse

Structural weaknesses

It was in this situation that the disintegration of the military 'theme' system, which had been the foundation of the empire's remarkable success from the eighth to eleventh centuries, revealed itself as a real catastrophe for the Byzantine state.

The first advantage of the theme system had been its numerical strength. It is thought that the Byzantine field army under Manuel I Komnenos (r. 1143–1180) had numbered some 40,000 men. However, there is evidence that the thematic armies of earlier centuries had provided the empire with a numerically superior force. The army of the theme of Thrakesion alone had provided about 9,600 men in the period 902–936, for example. Furthermore, the thematic armies had been stationed in the provinces, and their greater independence from central command meant that they were able to deal with threats quickly at a local level. This, combined with their greater numbers, allowed them to provide greater defense in depth.

The other key advantage of the theme system was that it had offered the Byzantine state good value for money. It provided a means of cheaply mobilising large numbers of men. The demise of the system meant that armies became more expensive in the long run, which reduced the numbers of troops that the emperors could afford to employ. The considerable wealth and diplomatic skill of the Komnenian emperors, their constant attention to military matters, and their frequent energetic campaigning, had largely countered this change. But the luck of the empire in having the talented Komnenoi to provide capable leadership was not a long-term solution to a structural problem in the Byzantine state itself.

After the death of Manuel I Komnenos in 1180, the Angeloi had not lavished the same care on the military as the Komneni had done, and the result was that these structural weakness began to manifest themselves in military decline. From 1185 on, Byzantine emperors found it increasingly difficult to muster and pay for sufficient military forces, while their incompetence exposed the limitations of the entire Byzantine military system, dependent as it was on competent personal direction from the emperor. The culmination of the empire's military disintegration under the Angeloi was reached on 13 April 1204, when the armies of the Fourth Crusade sacked Constantinople.

Conclusion

Thus, the problem was not so much that the Komnenian army was any less effective in battle (the thematic army's success rate was just as varied as that of its Komnenian counterpart); it is more the case that, because it was a smaller, more centralised force, the twelfth century army required a greater degree of competent direction from the emperor in order to be effective. Although formidable under an energetic leader, the Komnenian army did not work so well under incompetent or uninterested emperors. The greater independence and resilience of the thematic army had provided the early empire with a structural advantage that was now lost.

For all of the reasons above, it is possible to argue that the demise of the theme system was a great loss to the Byzantine empire. Although it took centuries to become fully apparent, one of the main institutional strengths of the Byzantine state was now gone. Thus it was not the army itself that was to blame for the decline of the empire, but rather the system that supported it. Without strong underlying institutions that could endure beyond the reign of each emperor, the state was extremely vulnerable in times of crisis. Byzantium had come to rely too much on individual emperors, and its continued survival was now no longer certain. While the theme system's demise did play a major role in the empire's military decline, other factors were important as well. These include:

• An increasing reliance on foreign mercenaries, which also contributed to the Byzantine Navy's decline.
• A long, slow decay in the quality and prestige of the ordinary, non-elite Byzantine infantry.
• A creeping Feudalism that helped to erode centralized administration.
• Increasing emulation of Western (or Latin) weapons, equipment and warfare methods, beginning especially during the reign of Manuel I Komnenos.

Armies of the successor states and of the Palaeologi

After 1204 the emperors of Nicaea continued some aspects of the system established by the Komneni. However, despite the restoration of the empire in 1261, the Byzantines never again possessed the same levels of wealth, territory and manpower that had been available to the Komnenian emperors and their predecessors. As a result, the military was constantly short of funds. After the death of Michael VIII Palaiologos in 1282, unreliable mercenaries such as the grand Catalan Company came to form an ever larger proportion of the remaining forces.

At the fall of Constantinople in 1453, the Byzantine army totaled about 7,000 men, 2,000 of whom were foreign mercenaries. Against the 80,000 Ottoman troops besieging the city, the odds were hopeless. The Byzantines resisted the third attack by the Sultan's elite Janissaries and according to some accounts on both sides were on the brink of repelling them, but a Genoan general in charge of a section of the defense, Giovanni Giustiniani, was grievously wounded during the attack, and his evacuation from the ramparts caused a panic in the ranks of the defenders. Many of the Italians, who were paid by Giustiniani himself, fled the battle.

Some historians suggest that the Kerkoporta gate in the Blachernae section had been left unlocked, and the Ottomans soon discovered this mistake – although accounts indicate that this gain for the Ottomans was in fact contained by defenders and pushed back. The Ottomans rushed in. Emperor Constantine XI himself led the last defense of the city by himself. Throwing aside his purple regalia, he stood in front of the oncoming Ottoman Turks with sword and shield in hand.

The emperor was struck twice by the Turk troops, the mortal blow being a knife to his back. There, on the walls of Constantinople, alone and abandoned by his remaining troops, the emperor died. The fall of the Byzantine capital meant the end of the Roman empire. The Byzantine army, the last surviving direct descendant of the Roman legions, was finished.

Manpower

The exact size and composition of the Byzantine army and its units is a matter of considerable debate, due to the scantness and ambiguous nature of the primary sources. The following table contains approximate estimates. All estimates excludes the number of oarsmen, for those estimates see Byzantine navy.

According to Mark Whittow the military resources of the Byzantine Empire were broadly comparable to those of other early medieval European states. As such Byzantium may not have been wealthier or more powerful than other European states, but it was more centralized and more united, and this was a vital factor in its survival. By using various Byzantine sources he estimates the entire cavalry forces of the empire, between the 8th and 10th centuries, were somewhere just over 10,000 and the number of infantry 20,000, and argues that the numbers of soldiers in Byzantine units should be numbered in the hundreds and not thousands, and the army in thousands and not tens of thousands. This however is argued by Warren Treadgold to be a result of incorrect reading of sources, such as confusing detachments of legions for the entire legions. The empire had demonstrable continuity of government and administration from antiquity until 1204, and had demonstrated a high degree of organization and standardization. Treadgold's analysis of sources finds that they support a Byzantine army that was "large and tightly organized" until its dissolution in the crisis of the 11th century. As such, the Middle Byzantine army was estimated to be significantly larger and was in no way comparable to contemporary Western European armies. Whittow's work shows many signs of carelessness and incorrect reading of sources.

Alexandru Madgearu cites an estimate of an army of 250,000 in 1025. Treadgold cites contemporary estimates of 80,000 in 773 and 120,000 in 840.