The power of the Eastern Roman Empire has again waned by 1185 because of external conflicts.

The noble brothers Asen and Peter lead a revolt that forces imperial recognition of an autonomous Bulgarian state.

Centered at Turnovo (present-day Veliko Turnovo), this state becomes the Second Bulgarian Empire.

Like the First Bulgarian Empire, the second expands at the expense of a preoccupied Byzantine Empire.

In 1202 Tsar Kaloian (1197-1207) concludes a final peace with Constantinople that gives Bulgaria full independence.

Kaloian also drives the Magyars from Bulgarian territory and in 1204 concludes a treaty with Rome that consolidates Bulgaria's western border by recognizing the authority of the pope.

By the middle of the thirteenth century, Bulgaria again rules from the Black Sea to the Adriatic.

Access to the sea greatly increases commerce, especially with the Italian Peninsula.

Turnovo becomes the center of Bulgarian culture, which enjoys a second golden age.

The final phase of Bulgaria's second Balkan dominance is the reign of Kaloian's successor, Ivan Asen II (1218-41).

In this period, culture continues to flourish, but political instability again threatens.

After the death of Ivan Asen II, internal and external political strife intensify.

Sensing weakness, the Tatars begin what will; be sixty years of raids in 1241, the Byzantines retake parts of the Second Bulgarian Empire, and the Magyars again advance.

The Greeks have ruled harshly over Bulgaria for nearly two centuries, using taxes and the political power of the church to crush opposition.

The first and second Crusades had passed through Bulgaria in this period, devastating the land.

In 1186, after a violent dispute with the new Greek emperor, Asen and Peter, descendants of Vlach landowners and boyars from Turnovo, whose family name is Belgun, lead a popular rising of Vlachs and Bulgarians and proclaim their independence from Constantinople.

Asen is crowned tsar as Ivan Asen I at Turnovo, and …

Constantinople's forces are thoroughly defeated in 1196 after nearly a decade of intermittent warfare between the Empire and Bulgaria.

Ivan Asen is killed later in this year by one of his boyars, Ivanko, who had been threatened with punishment for an affair with the sister of Ivan Asen I's wife.

The murderer attempts to assume control in Turnovo.

Petar Asen, Ivan’s brother, who had retired to Preslav without abdicating the throne, marches on Turnovo, besieges the Ivanko, and forces him to flee to Constantinople.

Peter is killed by the boyars a year after he ascends the Bulgarian throne.

His younger brother Kaloyan is then crowned tsar.

The Second Bulgarian Empire expands, like the first, at the expense of a preoccupied Constantinople.

In 1202, Tsar Kaloyan concludes a final peace with the Empire that gives Bulgaria full independence.

The foundations of the Second Bulgarian State, with Tarnovo as its capital, had been laid as a result of the successful uprising of the brothers Peter IV and Ivan Asen I in 1185/1186.

Following Boris I’s principle that the sovereignty of the state is inextricably linked to the autocephaly of the Church, the Asen brothers had immediately taken steps to restore the Bulgarian Patriarchate.

As a start, they established an independent archbishopric in Tarnovo in 1186.

The struggle to have the archbishopric recognized according to the canonical order and elevated to the rank of a Patriarchate will take almost fifty years.

Following the example of Boris I, Bulgarian Tsar Kaloyan, a younger brother and heir of Peter IV and Ivan Asen I, has maneuvered for years between the Patriarch of Constantinople and Pope Innocent III.

King Emeric of Hungary had invaded Bulgaria in 1202 and conquered the areas of Belgrade, Braničevo (Kostolac), and Niš (which he turned over to his protégé on the throne of Serbia, Vukan Nemanjić).

Kaloyan had retaliated in 1203, restoring Vukan's brother Stefan Nemanjić in Serbia and recovering his lands after defeating the Hungarians.

Ill feeling between Bulgaria and the Hungarians continues until the intercession of Pope Innocent III, who had written to Kaloyan, inviting him to unite his Church with the Roman Catholic Church, as early as 1199.

Wanting to bear the title of Emperor and to restore the prestige, wealth and size of the First Bulgarian Empire, Kaloyan had responded in 1202.

In this political maneuver, he had requested that Pope Innocent III bestow on him the imperial crown and scepter that had been held by Simeon I, Peter I, and Samuel and in exchange he might consider communication with Rome.

Kaloyan had also wanted the Papacy to recognize the head of the Bulgarian Church as a Patriarch.

The pope is not willing to make concessions on that scale, and when his envoy, Cardinal Leo, arrives in Bulgaria, he anoints the Archbishop Vasilij of Turnovo as Primate of Bulgarians and Vlachs.

Kaloyan only receives a Uniate crown as rex Bulgarorum et Blachorum ("King of Bulgarians and Wallachians") or rex Bulgarie et Blachie ("King of Bulgaria and Wallachia"), not emperor.

Blithely, Kaloyan writes to the pope, thanking him for an imperial coronation and for the anointing of his patriarch.

He also assures him that he too will follow the Catholic Church rites, as part of the agreement.

Meanwhile, in an attempt to foster an alliance with Kaloyan, Emperor Alexios III Angelos recognizes his imperial title and promises him patriarchal recognition.

The union with the Roman Catholic Church will continue or well over three decades.

Kaloyan, tsar of Bulgaria, had offered the crusaders an alliance against Constantinople, but his offer had been declined, and the new Latin Empire now expresses the intention of conquering all the lands of Constantinople’s former empire and its neighbors.

Having also driven the Magyars from Bulgarian territory, Kaloyan had concluded a treaty earlier in 1204 with Rome that has consolidated Bulgaria's western border by recognizing the authority of the pope, from whom he has received a royal crown.

However, when the patriarch at Constantinople again recognizes the independence of the Bulgarian church, Kaloyan reverts to Orthodoxy.

The Bulgarians remain hostile to the rump Empire based at Nicaea.

Ivan Asen II is a son of Ivan Asen I, one of the two founders of the Asen dynasty and the Second Bulgarian Empire, and Elena.

After the death of his uncle Kaloyan in 1207, Ivan Asen's cousin, Boril, had usurped the throne and forced him to flee to the Rus principality of Galicia-Volhynia.

Bulgaria’s alliance with the Latin Empire, the Kingdom of Hungary, and the Despotate of Epirus had dragged Boril into a war against Serbia, in which Boril has made little headway, especially after the murder of his brother Strez in 1215.

With the death of Henry in 1216 and the departure of Andrew II on the Fifth Crusade, Boril had been left essentially without strong supporters.

In 1217 or 1218 Ivan Asen, Boril's cousin, returns from exile with the support of Galicia-Volhynia and defeats Boril, who locks himself up in Tărnovo.

After a siege of perhaps seven months (rather than the "seven years" of the Byzantine sources), Boril flees the capital, which surrenders to Ivan Asen.

Boril is captured during his escape, and is blinded and relegated to a monastery.

Having established himself on the throne, Ivan Asen II sets about recovering the losses sustained by Bulgaria during the reign of Boril.

A good soldier and administrator, Ivan restores law and order, controlling the boyars.

The return of Andrew II of Hungary from the Fifth Crusade in 1218 had provided Ivan Asen II an opportunity to establish a marriage alliance and to obtain (probably in 1221) the return of the disputed territories of Belgrade on the Danube as the dowry of Princess Anna Maria of Hungary.

Ivan had also made an alliance with Theodore Komnenos Doukas of Epirus to his south, although the latter had expanded his control over various Bulgarian-inhabited territories, including Ohrid.

The alliance had been cemented with the marriage of Ivan Asen II's daughter to Theodore's brother Manuel.

After the death of Robert of Courtenay in 1228, the barons in Constantinople consider Ivan Asen II as a possible choice of regent or guardian of the minor Baldwin II.

By this time, Theodore of Epirus had reconquered Thessalonica from the Latin Empire in 1224, had had himself crowned emperor there by the autocephalous archbishop of Ohrid, had taken Adrianople, and is poised to strike at Constantinople itself.