There are several documented cases of Byzantine commanders abandoning an invasion because of a reluctance to confront the Bulgarian army on its home territory.

Its success under Tsar Simeon I the Great marked the creation of a wide-ranging empire, and its defeat in a prolonged war of attrition in the early 11th century meant the end of Bulgarian independence.

[7]The Bulgarian army was well armed according to the Avar model: the soldiers had a sabre or a sword, a long spear and a bow with an arrow-quiver on the back.

[8] The infantry of the newly formed state was composed mainly of Slavs, who were generally lightly armed soldiers, although their chieftains usually had small cavalry retinues.

In 680, the Byzantines under Constantine IV were crushed in the battle of Ongal and were forced to conclude a humiliating peace treaty by which they de jure acknowledged the formation of a Bulgarian state on their former territory.

After bloody fights between the Dnester and the Dneper rivers, the Khazar threat was eliminated but the founder of the Bulgarian state Khan Asparukh perished in one of the battles in 700.

During the first years of his reign, Khan Krum destroyed the Avar Khaganate and doubled Bulgaria's territory, taking over the fertile Pannonian Plain and the salt and gold mines of Transylvania.

After comparison with the data of Pseudo-Simeon, it can be assumed that the heavy cavalry component of the Bulgarian army numbered between 17–20,000 and 30,000 men, depending on the level of mobilization.

The first Byzantine attempts for counter-attack were repulsed after the annihilation of a 60,000[30] force in the battle of the Gates of Trajan in 986 in which Basil II himself barely escaped.

In the following decade the Bulgarians took Thessaly, destroyed the Principality of Duklja, advanced deep to the south as far as Corinth on the Peloponnese peninsula and campaigned in Dalmatia and Bosnia.

From 1001 onwards, Basil II launched yearly campaigns into Bulgarian territory, methodically taking important cities such as Preslav, Pliska and Vidin, and inflicting several defeats on Samuil.

The Byzantine historian Georgius Monachus Continuatus wrote that the Bulgarian army had 360,000 men, a greatly exaggerated number, the actual being 10 times smaller.

[34] The country was able to mobilize around 100,000 men in the first decade of the 13th century (Kaloyan reportedly offered the leader of the Fourth Crusade Baldwin I 100,000 soldiers to help him take Constantinople).

After a number of successful battles between 1185 and 1204, the Byzantine Empire was effectively driven from the lands it held in the northern Balkans, and the Imperial crown and cross.

After several setbacks under Boril I (1207–1218), Ivan Asen II decisively defeated the Despotate of Epirus in the battle of Klokotnitsa, in which the much smaller Bulgarian army outmaneuvered its enemy.

Feudal disunion and the widespread heretical movements such as Bogomilism, the Adamites or the Varlaamites did not allow the country to maintain a significant force.

The Bulgarians relied on their fortified cities and castles for defense, but due to the lack of a common leadership, coordination amongst them was feeble and they were defeated and occupied in detail.

For only one decade between 1354 and 1364 the Ottomans conquered virtually the whole of Thrace seizing large cities such as Plovdiv, Beroia, Dianopolis (Yambol) and Adrianople and defeating several small Bulgarian forces.

[45] In 1371 a large Bulgarian-Serb army under Vukašin Mrnjavčević and Jovan Uglješa, two feudal lords in Macedonia, was annihilated by the Ottomans under Lala Shahin Pasha at Chernomen and soon the Bulgarian Emperor had to admit the defeat and became a vassal to the invaders.

In 1393 the capital Tarnovo was besieged and seized by the Ottoman Turks and three years later fell Vidin – the last major Bulgarian city.

The Ottoman invasion was a disaster for the Bulgarian army — the nobility and the leaders of the nation were killed or emigrated and civilians were not allowed to have weapons until the 19th century.

Most of the nine campaigns of the ambitious Emperor Constantine V to eliminate the young Bulgarian state, which suffered political crisis, failed in the mountain passes of the Balkan.

The Bulgarians maintained many outposts and castles which guarded the passes and were able to locate an invading force and quickly inform the high command about any enemy moves.

Inside the fortress [Sofia] there is a large and elite army, its soldiers are heavily built, moustached and look war-hardened, but are used to consume wine and rakia – in a word, jolly fellows.

In several battles the Bulgarian troops waited the Byzantines for days until the latter attack — for instance at Marcelae (792) or Versinikia (813) – and scored decisive victories.

[50] After a successful battle the Bulgarian would pursue the enemy in depth in order to eliminate as much soldiers as possible and not to allow him to reorganize his forces quickly and effectively.

After the success at Anchialus in 917 the Byzantines were not given time to prepare their resistance properly and the result was the annihilation of their last forces in the battle of Katasyrtai.

During war the Bulgarians usually sent light cavalry to devastate the enemy lands on a broad front pillaging villages and small towns, burning the crops and taking people and cattle.

The Bulgarians used siege machines on a large scale for the first time during the reign of Khan Krum (803–814), when they employed Arab renegades to gain experience.

[62] During the 14th century the Bulgarian army increasingly relied on foreign mercenaries, which included Western knights, Mongols, Ossetians or came from vassal Wallachia.