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.

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.

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 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.

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.

[14] 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.

"[16] "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.

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."

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.

[21] 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.

[23] 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.

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.

The tagmata were exclusively heavy cavalry 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.

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.

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).

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.

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.

The Byzantine cavalry were ideally suited to combat on the plains of Anatolia and northern Syria, which, from the seventh century onwards, constituted the principal battleground in the struggle against the forces of Islam.

They were heavily armed using lance, mace and sword as well as strong composite bows which allowed them to achieve success against lighter, faster enemies, being particularly effective against both the Arabs and Turks in the east, and the Hungarians and Pechenegs in the west.

Wealthier soldiers might be able to afford iron lamellar or even chain mail, but these were generally the preserve of the cavalry and officers; many military manuals of the 10th and 11th centuries do not even mention infantry wearing these being a possibility.

Other barbarians included the Huns, who had invaded the divided Roman Empire during the second quarter of the 5th century under Attila, and the Gepids, who had settled in the Romanian territories north of the Danube River.

Additionally, during the Komnenian period, the mercenary units would simply be divided by ethnicity and called after their native lands: the Inglinoi (Englishmen), the Phragkoi (Franks), the Skythikoi (Scythians), the Latinikoi (Latins), and so on.

The tremendous fighting abilities of these axe-wielding, barbarian Northerners and their intense loyalty (bought with much gold) established them as an elite body, which soon rose to become the Emperors' personal bodyguard.

A myriad of swords of Byzantine manufacture have been found dating to the 9th–11th centuries in the Balkans and Pontic region, namely consisting of the types "Garabonc", "Pliska", and "Galovo" after their findspots.

[69] A myriad of axeheads have been found from sites such as the Drastar battlefield, primarily single-bladed, but one highly decorated example from the Novi Pazar region of Bulgaria possesses a war pick opposite the head, corroborating the descriptions in the military manuals.

Recurve composite bows of this period typically stood between 1.2 and 1.6 meters in length, like the 9th century examples from Moshchevaja Balka in the Caucasus, changing in form from Qum Darya-type (Hunnic), to Avar, to Magyar, to Seljuk as technology and cross-cultural contact progressed.

[70][71] The solenarion was a hollow tube through which an archer could launch several small darts (myas, i.e., "flies") rapidly using a thumb draw; Anna Komnene remarked that the Crusader's Western-type crossbow, which she called a tzangra, was unknown to Byzantium before the 12th century.

[88] The majority of lamellar armors in Europe from the 6th–7th centuries are of late Roman manufacture, which were gifted to and then found in the burials of Germanic and Avar nobles, although a handful were of local make.

The Traction Trebuchet is believed to have been carried over from China to Europe by the Avars in the 550s–580s AD, where it was quickly adopted by the late Roman army, calling it a manganikon or alakatia, hence the term "mangonel.

[107] Alongside trebuchets, the Tactica of Leo VI mentions the use of the toxobolistra, which is further described by the De Ceremoniis' section on the expeditions to Crete as being an iron-framed torsion engine the same as that from late antiquity.