The Bulgarian Empire and the Byzantine Empire fought a war from 913 until 927. Although the war was provoked by the Byzantine emperor Alexander's decision to discontinue paying an annual tribute to Bulgaria, the military and ideological initiative was held by Simeon I of Bulgaria, who demanded to be recognized as tsar and made it clear that he aimed to conquer not only Constantinople but the rest of the Byzantine Empire as well.
In 917, the Bulgarian army dealt a crushing defeat to the Byzantines at the Battle of Achelous, resulting in Bulgaria's total military supremacy in the Balkans. The Bulgarians again defeated the Byzantines at Katasyrtai in 917, Pegae in 921 and Constantinople in 922. The Bulgarians also captured the important city of Adrianople in Thrace and seized Thebes, capital of the Theme of Hellas, deep in southern Greece. Following the disaster at Achelous, Byzantine diplomacy incited the Principality of Serbia to attack Bulgaria from the west, but this assault was easily contained. In 924, the Serbs ambushed and defeated a small Bulgarian army on its way to Serbia, provoking a major retaliatory campaign that ended with Bulgaria's annexation of Serbia at the end of that year.
Simeon was aware that he needed naval support to conquer Constantinople and in 922 sent envoys to the Fatimid caliph Ubayd Allah al-Mahdi Billah in Mahdia to negotiate the assistance of the powerful Arab navy. The caliph agreed to send his own representatives to Bulgaria to arrange an alliance but his envoys were captured en route by the Byzantines near the Calabrian coast. Emperor Romanos I Lekapenos managed to avert a Bulgarian–Arab alliance by showering the Arabs with generous gifts. By the time of his death in May 927, Simeon controlled almost all Byzantine possessions in the Balkans, but Constantinople remained out of his reach.
In 927, both countries were exhausted by the huge military efforts that had taken a heavy toll on the population and economy. Simeon's successor Peter negotiated a favourable peace treaty. The Byzantines agreed to recognize him as emperor of Bulgaria and the Bulgarian Orthodox Church as an independent patriarchate, as well as to pay an annual tribute. The peace was reinforced with a marriage between Peter and Romanos's granddaughter Irene Lekapene. This agreement ushered in a period of 40 years of peaceful relations between the two powers, a time of stability and prosperity for both Bulgaria and the Byzantine Empire.
Prelude
Political background
In the first years after his accession to the throne in 893, Simeon successfully defended Bulgaria's commercial interests, acquired territory between the Black Sea and the Strandzha mountains, and imposed an annual tribute on the Byzantine Empire as a result of the Byzantine–Bulgarian war of 894–896. The outcome of the war confirmed Bulgarian domination in the Balkans, but Simeon knew that he needed to consolidate his political, cultural and ideological base in order to fulfil his ultimate goal of claiming an imperial title for himself and eventually assuming the throne in Constantinople. He implemented an ambitious construction programme in Bulgaria's new capital, Preslav, so that the city would rival the splendour of the Byzantine capital. Simeon continued the policy of his father Boris I (r. 852–889) of establishing and disseminating Bulgarian culture, turning the country into the literary and spiritual centre of Slavic Europe. The Preslav and literary schools, founded under Boris I, reached their apogee during the reign of his successor. It was at this time that the Cyrillic alphabet was invented, most likely by the Bulgarian scholar Clement of Ohrid.
The Magyar devastation of the country's north-eastern regions during the War of 894–896 exposed the vulnerability of Bulgaria's borders to foreign intervention under the influence of Byzantine diplomacy. As soon as the peace with Byzantium had been signed, Simeon sought to secure the Bulgarian positions in the western Balkans. After the death of the Serb prince Mutimir (r. 850–891), several members of the ruling dynasty fought over the throne of the Principality of Serbia until Petar Gojniković established himself as a prince in 892. In 897 Simeon agreed to recognize Petar and put him under his protection, resulting in a twenty-year period of peace and stability to the west. However, Petar was not content with his subordinate position and sought ways to achieve independence.
The internal situation of the Byzantine Empire at the beginning of the 10th century was seen by Simeon as a sign of weakness. There was an attempt to murder emperor Leo VI the Wise (r. 886–912) in 903 and a rebellion of the commander of the Eastern army Andronikos Doukas in 905. The situation further deteriorated as the emperor entered into a feud with the Ecumenical Patriarch Nicholas Mystikos over his fourth marriage, to his mistress Zoe Karbonopsina. In 907, Leo VI had the patriarch deposed.
Crisis of 904
At the beginning of the 10th century, the Arabs completed the conquest of Sicily and from 902 began attacking Byzantine shipping and towns in the Aegean Sea. In 904, they sacked the empire's second-largest city, Thessalonica, taking 22,000 captives and leaving the city virtually empty. Simeon decided to exploit that opportunity, and the Bulgarian army appeared in the vicinity of the deserted city. By securing and settling Thessalonica, the Bulgarians would have gained an important port on the Aegean Sea and would have cemented their hold on the western Balkans, creating a permanent threat to Constantinople. Aware of the danger, the Byzantines sent the experienced diplomat Leo Choirosphaktes to negotiate a solution. The course of the negotiations is unknown – in a surviving letter to emperor Leo VI the Wise, Choirosphaktes boasted that he had "convinced" the Bulgarians not to take the city but did not mention more details. However, an inscription found near the village of Narash testifies that since 904 the border between the two countries ran only 20 kilometres (12 mi) to the north of Thessalonica. As a result of the negotiations, Bulgaria secured the territorial gains acquired in Macedonia during the reign of Khan Presian I (r. 836–852) and expanded its territory further south, taking possession of most of the region. The western section of the Byzantine–Bulgarian border ran from the Falakro mountain through the town of Serres, which lay on the Byzantine side, then turned south-west to Narash, crossed the Vardar river at the modern village of Axiohori, ran through Mount Paiko, passed east of Edessa through the Vermio and Askio mountains, crossed the river Haliacmon south of the town of Kostur, which lay in Bulgaria, ran through the Gramos mountains, then followed the river Aoös until its confluence with the river Drino, and finally turned west, reaching the Adriatic Sea at the town of Himarë.
Beginning of the war and Simeon I's coronation
In 912 Leo VI died and was succeeded by his brother Alexander, who set about reversing many of Leo VI's policies and reinstated Nicholas Mystikos as patriarch. As the diplomatic protocol of the time prescribed, Simeon sent emissaries to confirm the peace in late 912 or early 913. According to the Byzantine chronicler Theophanes Continuatus, these emissaries said that Simeon "would honour the peace if he was to be treated with kindness and respect, as it was under emperor Leo. However, Alexander, overwhelmed by madness and folly, ignominiously dismissed the envoys, made threats to Simeon and thought he would intimidate him. The peace was broken and Simeon decided to raise arms against the Christians [the Byzantines]." Unlike his predecessors, Simeon's ultimate ambition was to assume the throne of Constantinople as a Roman emperor, creating a joint Bulgarian–Roman state. Alexander's provocative behavior furnished the Bulgarian ruler with a casus belli. However, the historian John Fine argues that Simeon had already planned an invasion before the failure of the embassy, judging the new Byzantine leadership to be weak: Alexander was unpopular, inexperienced and possibly alcoholic, and his successor Constantine VII was a sickly little boy, considered by many to be illegitimate. While Bulgaria was preparing for war, on 6 June 913 Alexander died, leaving Constantinople in chaos with an under-aged emperor under the regency of patriarch Mystikos.
The first steps of the regency were to attempt to divert Simeon's attack. Nicholas Mystikos sent a letter which, while praising the wisdom of Simeon, accused him of attacking an "orphan child" (i.e., Constantine VII) who had done nothing to insult him, but his efforts were in vain. Toward the end of July 913 the Bulgarian monarch launched a campaign at the head of a large army, and in August he reached Constantinople unopposed. The head of the Byzantine chancery, Theodore Daphnopates, wrote about the campaign fifteen years later: "There was an earthquake, felt even by those who lived beyond the Pillars of Hercules." The Bulgarians besieged the city and constructed ditches from the Golden Horn to the Golden Gate at the Marmara Sea. Since Simeon had studied at the University of Constantinople and was aware that the city was impregnable to a land attack without maritime support, those actions were a demonstration of power, not an attempt to assault the city. Soon, the siege was lifted and kavhan (first minister) Theodore Sigritsa was sent to offer peace. Simeon had two demands – to be crowned Emperor of the Bulgarians and to betroth his daughter to Constantine VII, thus becoming father-in-law and guardian of the infant emperor.
After negotiations between Theodore Sigritsa and the regency, a feast was organised in honour of Simeon's two sons in the Palace of Blachernae presided over personally by Constantine VII. Patriarch Nicholas Mystikos went to the Bulgarian camp to meet the Bulgarian ruler in the midst of his entourage. Simeon prostrated himself before the Patriarch, who instead of an imperial crown placed upon Simeon's head his own patriarchal crown. The Byzantine chronicles, who were hostile to Simeon, had presented the ceremony as a sham, but modern historians, such as John Fine, Mark Whittow and George Ostrogorsky, argue that Simeon was too experienced to be fooled and that he was indeed crowned Emperor of the Bulgarians (in Bulgarian, Tsar). The sources suggest that Nicholas Mystikos also agreed to Simeon's second condition, which could have paved Simeon's route to become co-emperor and eventually emperor of the Romans. Having achieved his goal, Simeon returned to Preslav in triumph, after he and his sons were honoured with many gifts. To mark this achievement, Simeon changed his seals to read "Simeon, peacemaking emperor, [may you reign for] many years".
Battle of Achelous
The agreement concluded in August 913 proved to be short-lived. Two months later, Constantine VII's mother, Zoe Karbonopsina, was allowed to return to Constantinople from exile. In February 914 she overthrew the regency of Nicholas Mystikos in a palace coup. Mystikos reluctantly proclaimed her as empress, and retained his Patriarchal title. Her first order was to revoke all concessions given to the Bulgarian monarch by the regency, provoking military retaliation. In the summer of 914 the Bulgarian army invaded the themes of Thrace and Macedonia. Simultaneously, the Bulgarian troops penetrated into the regions of Dyrrhachium and Thessalonica to the west. Thrace's largest and most important city, Adrianople, was besieged and captured in September and the local population recognized Simeon as its ruler. However, the Byzantines promptly regained the city in exchange for a huge ransom.
To deal with the Bulgarian threat for good, the Byzantines took measures to end the conflict with the Abbasid Caliphate in the east and attempted to create a wide anti-Bulgarian coalition. Two envoys were sent to Baghdad, where they secured peace with caliph al-Muqtadir in June 917. The strategos of Dyrrhachium, Leo Rhabdouchos, was instructed to negotiate with the Serbian prince Petar Gojniković, who was a Bulgarian vassal but was willing to renounce Bulgarian suzerainty. However, the court in Preslav was warned about the negotiations by prince Michael of Zahumlje, a loyal ally of Bulgaria, and Simeon was able to prevent an immediate Serb attack. The Byzantine attempts to approach the Magyars were also successfully countered by the Bulgarian diplomacy. The general John Bogas was sent with rich gifts to the Pechenegs, who inhabited the steppes to the north-east of Bulgaria. The Bulgarians had already established strong connections with the Pechenegs, including through marriages, and Bogas' mission proved to be a hard one. He did manage to convince some tribes to send aid, but eventually the Byzantine navy refused to transport them to the south of the Danube river, probably as a result of the jealousy that existed between Bogas and the ambitious admiral Romanos Lekapenos.
...And even now there could be seen piles of bones at Anchialus, where the fleeing army of the Romans was disgracefully slain.
— from Leo the Deacon's History, 75 years after the battle of Achelous.
The Byzantines were forced to fight alone, but the peace with the Arabs allowed them to amass their whole army, including the troops stationed in Asia Minor. These forces were placed under the command of the Domestic of the Schools Leo Phokas the Elder. Before marching to battle the soldiers bowed to "the life-giving True Cross and vowed to die for one another". With his western and northern borders secure, Simeon was also able to muster a large host. The two armies clashed on 20 August 917 near the Achelous river in the vicinity of Anchialus. Initially, the Byzantines were successful, and the Bulgarians began an orderly retreat, but when Leo Phokas lost his horse, confusion spread among the Byzantine troops, who according to the chronicler John Skylitzes had low morale. Simeon, who was monitoring the battlefield from the nearby heights, ordered a counter-attack and personally led the Bulgarian cavalry. The Byzantine ranks broke and in the words of Theophanes Continuatus "a bloodshed occurred, that had not happened in centuries". Almost the whole Byzantine army was annihilated and only a few, including Leo Phokas, managed to reach the port of Messembria and flee to safety on ships.