The Slavic language replaces Greek, as a result of the intensive work of the Slav scholars, in Bulgarian church services and in literary life and becomes Bulgaria's official language.

Bulgaria's conversion has a political dimension, for it contributes both to the growth of central authority and to the melding of Bulgars and Slavs into a unified Bulgarian people.

Boris has adopted Greek Orthodox political conceptions, referring to himself as ruler “by the grace of God,” and the new religion provides justification for suppressing those boyars of Bulgar origin who cling to paganism and the political and social order with which it is linked.

After a reign of thirty-six years, Boris, whose faith apparently is deep and genuine, abdicates in 889 and becomes a monk, but he retains the right to take an active part in the government of the state.

His successor,Vladimir-Rasate, is the oldest of Boris-Mihail's sons and possibly the only one of them who had been born before Boris' adoption of Christianity.

According to Emperor Constantine VII Porphyrogenitos, Vladimir had taken part in a Bulgarian invasion of the Serbian lands, predating the Christianization of Bulgaria.

Another Bulgarian-Byzantine war begins in 889, this time over trade rights.

The little we know about the reign of Boris' eldest son and heir, Vladimir, Knyaz of Bulgaria, includes a military alliance he concludes in 892 with the East Frankish (German) King Arnulf of Carinthia against Great Moravia which, having in mind the interests of the Empire, is indirectly aimed against Constantinople.

This is a serious straying from the pro-imperial policy of his father, Boris I. Vladimir has become the instrument of a pagan reaction and a leader of the opponents of Slavic letters and literature.

Vladimir is mainly remembered for his attempt to eliminate Christianity in Bulgaria and the reinstitution of paganism.

This event is written of by Constantine of Preslav in his Didactic Gospel.

Vladimir starts the process of destroying the Christian temples and persecuting the clergymen, because he regards them as instruments of Constantinople and its efforts to influence the Bulgarian kingdom.

However, Vladimir Rasate's actions are not well received by the population and the aristocracy, and he is supported by only a few of the boyars.

Simeon was born in 864 or 865, as the third son of Knyaz Boris I of Krum's dynasty.

As Boris was the ruler who had Christianized Bulgaria in 865, Simeon has been a Christian all his life.

Because his eldest brother Vladimir had always designated heir to the Bulgarian throne, Boris had intended Simeon to become a high-ranking cleric, possibly Bulgarian archbishop, and had sent him to the University of Constantinople to receive theological education when he was thirteen or fourteen.

He had taken the name Simeon as a novice in a monastery there.

During the decade (from about 878 to 888) he spent in the imperial capital, he had received an excellent education and studied the rhetoric of Demosthenes and Aristotle.

He had also learned fluent Greek, to the extent that he is referred to as "the half-Greek" in Byzantine chronicles.

He is speculated to have been tutored by Patriarch Photios I of Constantinople, but this is not supported by any source.

Around 888, Simeon had returned to Bulgaria and settled at the newly established royal monastery of Preslav, where, under the guidance of Naum of Preslav, he has engaged in active translation of important religious works from Greek to Old Church Slavonic (Old Bulgarian), aided by other students from Constantinople.

Meanwhile, Vladimir had succeeded Boris, who had retreated to a monastery, as ruler of Bulgaria.

Vladimir has attempted to reintroduce paganism in the empire and possibly signed an anti-Constantinople pact with Arnulf of Carinthia, forcing Boris to reenter political life.

With the aid of loyal boyars and the army, Boris drives his dissolute son from the throne and has him blinded, unfitting him for rule.

He then convenes a council that confirms Christianity as the religion of the state and moves the administrative capital from Pliska to the Slavic town of Preslav to better cement the recent conversion.

The assembly also proclaims Bulgarian as the only language of state and church.

It is not known why Boris did not place his second son, Gavril, on the throne, but instead preferred Simeon.

Boris now retires permanently to monastic life, making generous grants to the Bulgarian Church and patronizing Slav scholarship.

The long-lasting peace with the Empire established by Simeon's father is about to end.

A conflict arises when Emperor Leo VI the Wise, allegedly acting under pressure from his mistress Zoe Zaoutzaina and her father Stylianos Zaoutzes, moves the marketplace for Bulgarian goods from Constantinople to Thessaloniki, where the Bulgarian merchants are heavily taxed.

The Bulgarians seek the protection of Simeon, who in turn complains to Leo.

However, the emperor ignores his embassy.

Forced to take action, Simeon invades the Empire from the north in the autumn of 894, meeting with little opposition due to the concentration of most imperial forces in eastern Anatolia to counter Arab invasions.

Informed of the Bulgarian offensive, the surprised Leo sends an army consisting of guardsmen and other military units from the capital to halt Simeon, but his troops are routed somewhere in the theme of Macedonia.

The Bulgarians take most of the Khazar mercenary guardsmen prisoners and kill many archons, including the army's commander.

However, instead of continuing his advance to the capital, Simeon quickly withdraws his troops to face a Magyar invasion from the north.

Bulgarian historians will later call these events "the first trade war in medieval Europe.”

The Magyars, as mounted nomads in contact with and often in alliance with Turkic tribes, have moved westward under Árpád and Kukszan, with one group following the Lower Danube valley and two other groups crossing the Carpathian passes, one of which enters into Transylvania in 895.

Having elected as their chief Árpád, the leader of their most powerful tribe, the Magyars cross the Carpathians en masse, probably in 895, and easily subjugate the peoples of the sparsely inhabited central plain, their first place of settlement.

Thought of as returning Huns, the Magyars come to be known as Hungarians.

Constantinople, unable to effectively respond to the Bulgarian campaign due to the engagement of its forces against the Arabs, persuades the Magyars to attack Bulgaria, promising to transport them across the Danube using the imperial navy.

Leo VI may have also concluded an agreement with Arnulf to make sure that the Franks do not support Simeon against the Magyars.

In addition, the talented commander Nikephoros Phokas is called back from southern Italy to lead a separate army against Bulgaria in 895 with the mere intention to overawe the Bulgarians.

Simeon, unaware of the threat from the north, rushes to meet Phokas' forces, but the two armies do not engage in a fight.

Instead, Constantinople offers peace, informing him of both the imperial foot and maritime campaign, but intentionally does not notify him of the planned Magyar attack.

Simeon does not trust the envoy and, after sending him to prison, orders the imperial navy's route into the Danube closed off with ropes and chains, intending to hold it until he has dealt with Phokas.

Despite the problems they encounter because of the fencing, the imperial forces ultimately manage to ferry the Magyar forces led by Árpád's son Liüntika across the Danube, possibly near modern Galaţi, and assists them in pillaging the nearby Bulgarian lands.

Once notified of the surprise invasion, Simeon heads north to stop the Magyars, leaving some of his troops at the southern border to prevent a possible attack by Phokas.

Simeon's two encounters with the enemy in Northern Dobruja result in Magyar victories, forcing him to retreat to Drǎstǎr.

The Magyars, after pillaging much of Bulgaria and reaching Preslav, return to their lands, but not before Simeon has concluded an armistice with Constantinople towards the summer of 895.

A complete peace is delayed, as Leo VI requires the release of the imperial captives from the Trade War.

The Bulgarian tsar, using a Magyar invasion in the lands of the neighboring Slavs in 896 as a casus belli, heads against the Magyars together with his Pecheneg allies and his father Boris I, who leaves the monastery for this occasion.

Gathering an enormous army, Tsar Simeon marches to the north eastern borders of the country.

He orders three days of fasting, saying that the soldiers should repent for their sins and seek help in God.

When this is done, the battle of Southern Buh, near the banks of the eponymous river, in modern Ukraine, begins.

It is long and unusually fierce but in the end the Bulgarians are victorious, defeating the Magyars completely and making them leave Etelköz forever to settle in Pannonia.

A third group of Magyars crosses into Carpathian Rus’ in 896.

Conquering the sparsely settled Carpathian Basin, they subjugate the resident Slavs and Vlachs there.