The Tang Empire, aided by Muslims in the west and the Bai kingdom of Nanzhao in the south, has fought intermittently with the Tibetan Empire for control of areas in Inner and Central Asia, which has at times been settled with marriage alliances.

There had been a long string of conflicts with Tibet over territories in the Tarim Basin between 670–692, and in 763, the Tibetans had even captured Chang'an for fifteen days amid the An Shi Rebellion.

Hostilities continue until 821, when a formal peace treaty is finally signed between the Tang Dynasty and the Tibetan Empire.

A bilingual inscription on a stone pillar outside the Jokhang temple in Lhasa records the terms of this treaty, including the borders between the two countries.

Thomas, standing as champion to the poor and with the support of al-Ma'mun, marches west in spring 821 at the head of a motley force of Caucasian peoples whose sole bonds are to be found in their devotion to iconodule doctrine and their hatred of Michael's Iconoclasm.

In his account of the revolt, the historian Genesius lists a variety of peoples from whom the armies of the rebel were drawn: Saracens, Abasgians, Getae, Alans, Chaldoi, Armenians, Vandals and adherents of heretical sects of the Paulicians and Athinganoi.

Within a matter of months, only two themes in Asia Minor remain loyal to Michael, and in December 821, Michael besieges Constantinople.

The royal faction, after a month's fighting, is in 822 able to regain much of the territory that Kim Heon-chang's forces had taken.

After the fall of Gongju, which had been the center of the rebellion, Kim Heon-chang takes his own life.

Caliph Al-Ma'mun, showing himself to be a judicious sovereign, closely controls his ministers and does not again appoint an all-powerful vizier.

He also tries to maintain strict control over the provincial governors but is forced to allow a relative degree of autonomy to his former general, Tahir, who had been named governor of Khurasan.

He rules independently of Baghdad, not even mentioning the caliph's name in Friday prayers in recognition of caliphal authority.

Thomas unsuccessfully attacks Constantinople, while his fleet is destroyed by Michael's navy using Greek fire.

His army unable to breach the walls of the great city, Thomas is forced to retreat due to weather and a Bulgar army attacking him.

The many tribes—Danes, Obotrites, Slovenes, Bretons, Basques—that inhabit the frontier lands at the start of the reign of Louis the German over Eastern Francia had remained in awe at the power of the Frankish emperor and dared not stir up any trouble.

The Sorbs in 818 had rebelled, however, and had been quickly followed by Slavomir, chief of the Obotrites, who had been captured and abandoned by his own people, being replaced in 818 by Ceadrag.

Soon, Ceadrag too had turned against the Franks and allied with the Danes, who will shortly become the greatest menace of the Franks.

A greater Slavic menace is gathering on the southeast, where, Ljudevit Posavski, the Croat Prince of Savia from about 810, is harassing the border at the Drava and Sava rivers.

As the ruler of the Pannonian Croats, his successful resistance of Frankish domination is an important precursor to the eventual unification of Croatian duchies in Dalmatia and Pannonia into the Kingdom of Croatia.

The margrave of Friuli, Cadolah, had been sent out against him, but he had died on campaign and in 820 his margarvate had been invaded by Slovenes.

An alliance had been made in 821 with Borna, duke of Dalmatia, and in 822 Ljudevit is brought to heel.

After being forced to flee, Ljudevit becomes a ruler over the Serbs, maintaining close ties with the Carantanians and Timokians (the Slavs, or Vlachs, in the Timok River valley).

Abd ar-Rahman II, who succeeds his father, al-Hakam I, as Emir of Córdoba in 822, will spend much of his thirty-year reign in nearly continuous warfare against Alfonso II of Asturias.

The Tragic Fate of Bernard of Italy and Emperor Louis the Pious’ Penance (810–822)

In 810, Bernard, the illegitimate son of King Pepin, Charlemagne’s third son, is appointed King of Italy, ruling as a vassal to the Carolingian Emperor. However, after Charlemagne’s death in 814, his successor, Louis the Pious, restructures the empire, prioritizing his own legitimate sons.

Bernard’s Rebellion and the Aftermath (817–818)

• In 817, Louis issues the Ordinatio Imperii, a succession plan that grants Italy to his eldest son, Lothair I, effectively disinheriting Bernard.
• Feeling his position endangered, Bernard rebels with the support of Bishop Theodulf of Orléans, fearing loss of autonomy under Lothair’s rule.
• Louis, acting swiftly, marches into Italy, forcing Bernard to submit.
• Bernard, trusting a safe-conduct guarantee, meets with the emperor but finds himself convicted without realizing he was on trial.

The Blinding and Death of Bernard (818)

• Louis orders Bernard blinded, a common Byzantine-inspired punishment meant to disable political rivals without executing them outright.
• The blinding procedure proves fatal, and Bernard dies in Milan soon after.
• This event deeply grieves Louis, who, as a devout Christian, recognizes the cruelty of his actions.

Louis the Pious’ Penance at Attigny (822)

Tormented by guilt, Louis performs public penance at his palace in Attigny, near Vouziers in the Ardennes, before:

• Pope Paschal I,
• A council of ecclesiastics, and
• The Frankish nobility.

As part of his atonement, he reconciles with Bernard’s three younger half-brothers:

• Hugo, later Abbot of St-Quentin,
• Drogo, soon made Bishop of Metz,
• Theodoric, whose career remains less well-documented.

The Political Consequences of Penance

Louis’ act of contrition, modeled after Theodosius the Great’s penance after the Massacre of Thessalonica (390), severely undermines his prestige as emperor:

• Frankish rulers were expected to be strong and decisive, not to confess their failures publicly.
• His humility is perceived as weakness, emboldening his sons and noble factions to challenge his authority.
• His public admission of minor offenses, unnecessary for a secular ruler, further damages his reputation among the aristocracy.

The Long-Term Impact

Louis’ penance at Attigny contributes to the later revolts against his rule, as dynastic strife and noble resistance weaken his hold on the empire. The event symbolizes the increasing power of the Church over secular rulers, foreshadowing future conflicts between emperors and religious authorities in medieval Europe.

Rabanus Maurus, a Frankish Benedictine monk born of noble parents in Mainz, had in 822 become abbot of the Monastery at Fulda.

The author of the encyclopaedia On the Nature of Things, he has also written treatises on education and grammar and commentaries on the Bible; he will be remembered as one of the most prominent teachers and writers of the Carolingian age.

The name Frankfurt first appears in writing in the year 794, when a letter from the Emperor to the bishop of Toledo contained "in loco celebri, qui dicitur Franconofurd," which reads "that famous place, which is called Frankfurt."

Emperor Louis makes the city of Frankfurt-am-Main his headquarters, and has a large palace erected there in 822. (Today a European banking metropolis, Frankfurt is the largest city in the German state of Hesse and the fifth-largest city in Germany.)