The Byzantine-Bulgarian wars were a series of conflicts fought between the Byzantines and Bulgarians which began when the Bulgars first settled in the Balkan peninsula in the 7th century, and intensified with the expansion of the Bulgarian Empire to the southwest after 800 AD. The Byzantines and Bulgarians continued to clash over the next century with variable success, until the Bulgarians, led by Krum, inflicted a series of crushing defeats on the Byzantines. After Krum died in 814, his son Omurtag negotiated a thirty-year peace treaty. In 893, during the next major war, Simeon I, the Bulgarian emperor, defeated the Byzantines while attempting to form a large Eastern European Empire, but his efforts failed.
Pomorie is a town and seaside resort in southeastern Bulgaria, located on a narrow rocky peninsula in Burgas Bay on the southern Bulgarian Black Sea Coast. It is situated in Burgas Province, 20 km away from the city of Burgas and 18 km from the Sunny Beach resort. The ultrasaline lagoon Lake Pomorie, the northernmost of the Burgas Lakes, lies in the immediate proximity. The town is the administrative centre of the eponymous Pomorie Municipality. Pomorie is an ancient city and today an important tourist destination. Pomorie was founded by the Ancient Greeks under the name Anchialos deriving from Ancient Greek "anchi-" ("near, close to") and "als-" (either "salt" word for "sea"). In Latin, this was rendered as Anchialus. The Bulgars called the town Tuthom, though it's more common name in Bulgarian was Анхиало, Anhialo based on the Greek name. During the Ottoman rule, the town was called Ahyolu. In 1934 the town was renamed to Pomorie, from the Bulgarian "po-" ("by, next to") and "more" ("sea"), corresponding to one of the two etymologies of the original Greek name. Possibly founded in the 5th or 4th century BC as a colony of Apollonia (Sozopol), Anchialos was mentioned in Strabo 's Geographica as a small town. It was briefly captured by Messembria in the 2nd century BC, but reconquered by Apollonia and its fortified walls destroyed. The western Black Sea coast was ultimately conquered by the Romans under Marcus Licinius Crassus in 29-28 BC after continuous campaigns in the area since 72-71. The fortified wall was meanwhile rebuilt, as evidenced by Ovid in 9 AD en route to Tomis. In the early 1st century AD Anchialos was the centre of a strategia of the vassal Odrysian kingdom, and the town had a Thracian population in the 6th century AD according to the early Byzantine historian Procopius. As the Odrysian kingdom's self-independence was abolished in 45 AD, Anchialos became part of the Roman province of Thrace and was formally proclaimed a city under Emperor Trajan. At the time the city controlled a vast territory bordering that of Augusta Trajana (Stara Zagora) and reaching the Tundzha to the west, bordering that of Messembria to the north and the southern shore of Lake Burgas to the south. Anchialos acquired the appearance of a Roman city and throve in the 2nd and 3rd century under the Severan Dynasty, serving as the most important import and export station of Thrace.
However, the invasion of barbarian tribes from the north meant an end to this prosperity in the middle of the 3rd century, with the Goths briefly capturing Anchialos around 270. Diocletian stayed in the city between 28 and 30 October 294. His and Constantine the Great 's reforms restored the city's prosperity for a while, as the proximity to the new capital of Constantinople made Anchialos a key food supply centre. Theodoric the Great passed through the city in 476 on the way to Adrianople. A high-ranking Byzantine general named Vitalian in 513 revolted in the region and briefly took control of Anchialos and the neighbouring cities to use their fleet in his attack of Constantinople until he was crushed in 515. The bishopric of Anchialus was originally a suffragan of the metropolitan see of Hadrianopolis in Haemimonto, capital of the Roman province of Haemimontus. However, the Notitiae Episcopatuum of Pseudo-Epiphanius, written in the reign of Byzantine Emperor Heraclius (c. 640), gives it as an autocephalous archbishopric, today listed by the Catholic Church as a titular see. The first bishop of the see whose name is known is 2nd-century Sotas, mentioned by Eusebius of Caesarea as an adversary of Montanism. Timotheus was at the Council of Sardica in 343/344. Sebastianus was one of the bishops at the First Council of Constantinople of 381. Sabbatius was a signatory of the decree of the Patriarch of Constantinople against simoniacs in 459. Paulus was at the Second Council of Constantinople in 553. Jacobus was a contemporary of Patriarch Tarasios of Constantinople. Nicolaus was at the Photian Council of Constantinople (879). No longer a residential bishopric, Anchialus is today listed by the Catholic Church as a titular see. The Slavic and Avar invasion in 584 meant Anchialos was conquered and its fortifications were destroyed. Avar Khagan Bayan turned the city into his residence for a few months and concluded a peace treaty with the Byzantines. At the eve of his campaigns, the emperor Maurice visited the city to oversee reconstruction.
After 681 and the formation of the First Bulgarian kingdom to the north Anchialos played an important role in many conflicts between the two empires. In 708 the forces of Justinian II were completely defeated near the fortress by the army of Bulgar Khan Tervel. On 30 June 763 the Bulgars under Telets suffered a defeat by the Byzantine army of Constantine V. On 21 June 766 the same emperor's fleet of 2,600 heavy ships sank en route to Anchialos, where Constantine was waiting, and most soldiers drowned, forcing him to return to Constantinople. In May 783 Irene undertook a demonstrative campaign across Thrace and restored Anchialos' destroyed fortifications. The city was first conquered by the Bulgarian Empire in 812, under Khan Krum, who settled Slavs and Bulgars in Anchialos. The Byzantines restored their control over the city and the area in 864. The Battle of Anchialus took place near the city on 20 August 917, and was one of Tsar Simeon the Great's greatest military achievements. Simeon's army routed the considerably larger Byzantine forces under Leo Phocas. Bulgaria retained the city until 971, when the Byzantine Empire reconquered it and held it for two centuries as Bulgaria was subjugated. After the restoration of the Bulgarian state Anchialos changed hands several times until it was captured by the Venetian knights of Amadeus VI, Count of Savoy in October 1366. The next year it was ceded to Byzantium. After the Ottoman invasion of the Balkans in the 14th century, Anchialos remained a Byzantine bulwark until submission in 1453 together with Constantinople.
The Battle of Achelous or Acheloos (the Battle of Anchialus) took place on 20 August 917, on the Achelous river near the Bulgarian Black Sea coast, close to the fortress Tuthom between Bulgarian and Byzantine forces. The Bulgarians obtained a decisive victory which not only secured the previous successes of Simeon I but made him de facto a ruler of the most Balkan Peninsula excluding the well-protected Byzantine capital Constantinople and southern Greece. The battle was one of the worst disasters ever to befall a Byzantine army, and conversely one of the greatest military successes of Bulgaria. Among the most significant consequences was the official recognition of the royal title of Tsar (Caesar) of the Bulgarian monarchs, and the consequent affirmation of Bulgarian equality vis-à-vis Byzantium. After the Bulgarian victory in the War of 894-896 the Byzantines were forced to pay tribute to Tsar Simeon I of Bulgaria. In 912 when the Byzantine emperor Leo VI died, his brother Alexander refused to pay tribute to the Bulgarians. Simeon saw an opportunity to wage a new war and fulfill his ambitions to conquer Constantinople. Alexander died in the same year and the new government under the Patriarch Nicholas Mystikos made desperate attempts to avoid the war, promising that the infant Emperor Constantine VII would marry one of Simeon's daughters. The patriarch and Simeon even met outside the walls of Constantinople, performing a coronation ceremony. Thereafter, Simeon began using the title "Tsar of the Bulgarians", and the Greek title basileus in his seals. After a plot in the Byzantine court in 914 however, the new regent Zoe, Constantine's mother, rejected the marriage. In answer the Bulgarians raided Eastern Thrace. Adrianople opened its gates to Simeon in September 914, and its population recognised Simeon as their ruler, while the Byzantine army was occupied in the east. In the next year the Bulgarian armies attacked the areas of Dyrrhachium and Thessalonica. Both sides carefully prepared for a decisive end of the conflict. Empress Zoe wanted to swiftly make a peace settlement with the Arabs and to engage the whole army of the East in a war with Simeon and destroy him. The Byzantines tried to find allies and sent emissaries to the Magyars, Pechenegs and Serbs but Simeon was familiar with the methods of Byzantine diplomacy and from the very beginning took successful actions to subvert a possible alliance between his enemies. Thus the Byzantines were forced to fight alone. By 917, after a series of successful campaigns, the Byzantine empire had stabilized its eastern borders, and the generals John Bogas and Leo Phocas were able to gather additional troops from Asia Minor, to reinforce the imperial tagmata and the European thematic troops, gathering a force of some 30,000 to 62,000 men. This was a very large army by contemporary standards, and its goal was the elimination of the Bulgarian threat from the north. The Byzantine commanders were convinced that their strategy would be successful. Morale was raised as the soldiers vowed by the miraculous Cross to die for one another. The spirit of the army was further raised as the troops were paid in advance and a fleet commanded by Romanus Lecapenus set off to the north at the mouth of the Danube. The Byzantines had tried to pay some Pecheneg tribes to attack, but Romanus would not agree to transport them across the Danube, and instead they attacked Bulgarian territory on their own. The Byzantine army marched northwards and set its camp in the vicinity of the strong fortress of Anchialus. Leo Phocas intended to invade Moesia and meet the Pechenegs and Lecapenus's troops in Dobrudzha. Simeon swiftly concentrated his army on the heights around the fortress. On the morning of 20 August 917, the battle between the Bulgarians and the Byzantines began by the river Achelous near the modern village Acheloi, 8 kilometers to the north of Anchialus on Bulgaria 's Black Sea coast. The Byzantine generals planned to outflank the right Bulgarian wing in order to detach Simeon's troops from the Balkan Passes. The Bulgarian ruler concentrated his most powerful forces in the two wings and left the centre relatively weak in order to surround the enemy when the centre would yield to the Byzantine attack. Simeon himself was in charge of large cavalry reserves hidden behind the hills which were intended to strike the decisive blow.Some Byzantines tried to repulse the cavalry charge but they were also attacked by the infantry. Tsar Simeon personally took part in the fight, his white horse killed at the height of the battle. The Byzantines were completely routed. Leo Phocas was saved by fleeing to Mesembria in Bulgaria, but in the thick of the battle Constantine Lips, John Grapson and many other commanders (archontes) were cut down along with an enormous number of soldiers and officers. By the end of the day the Bulgarians overwhelmed the defenders of Mesembria and captured the town. Leo Phocas barely escaped by boarding a ship. The Byzantine historian Leo the Deacon says that 75 years after this military catastrophe the field at Anchialus was still covered with tens of thousands of Roman skeletons. The battle was among the bloodiest of medieval history and some historians refer to it as "the battle of the century". The remainder of the Byzantine army fled all the way back to Constantinople, followed by the Bulgarians. Several days later Phokas was defeated once more at Katasyrtai where the last Byzantine troops were routed after a night fight. The battle of Katasyrtai occurred in the fall of 917, shortly after the striking Bulgarian triumph at Achelous near the village of the same names close to the Byzantine capital Constantinople. The result was a Bulgarian victory. While the victorious Bulgarian army was marching southwards, the Byzantine commander Leo Phokas, who survived at Achelous, reached Constantinople by sea and gathered the last Byzantine troops to intercept his enemy before reaching the capital. The two armies clashed near the village of Katasyrtai just outside the city and after a night fighting, the Byzantines were completely routed from the battlefield. The last Byzantine military forces were literally destroyed and the way to Constantinople was opened. The way to Constantinople was clear. The Byzantines proposed a new peace treaty, and Simeon entered the imperial city and was crowned for a second time as " Tsar" (Caesar) "of all Bulgarians and Romans". Simeon also demanded that his daughter would marry Constantine VII, the son of empress Zoe Karvounopsina, but Zoe refused and allied with Serbia and Hungary against him. However, in August 918, the general Romanus Lecapenus engineered a coup to depose Zoe and confined her to the monastery of St Euphemia-in-Petrium, allowing him to assume the purple. The alliance with the Serbs postponed the decisive assault of Constantinople. Simeon decided to secure his rear and sent an army under Marmais and Theodore Sigritsa to destroy them. His generals captured the Serb prince but that gave the Byzantines precious time to recover. The battle of Achelos was one of the most important battles in the long Byzantine-Bulgarian Wars. It foiled Byzantine designs on Bulgaria, secured the concession of the Caesar title to the Bulgarian rulers, and thereby firmly established Bulgaria's role as a key player in Europe. However, the dynastic marriage that Simeon desired to establish with the Byzantine imperial family was foiled. After his death in 927 however, his successor Peter I was able to secure the hand of Maria Lecapene, the granddaughter of emperor Romanus I, and with it an annual tribute, the renewed recognition of his Caesar title and the autocephaly of the Bulgarian church. This agreement ushered an unprecedented period of 40 years of peaceful relations between the two powers, a time of stability and prosperity for Bulgaria.