Constantine and Methodius, to facilitate the task of preaching in the vernacular and translating the Bible into the unwritten Slavic language, invent a script, initially known as Glagolitic, using the phonetic peculiarities of the Slavic tongue.

German leaders, however, want to enforce the use of the Latin liturgy among the Slavs, and the brothers are called to Rome to defend themselves.

After some two and a half years among the Moravians, the two brothers journey to Rome to ask for papal support for their work and their use of the Slavic language.

Constantine enters a convent in Rome, taking the name of Cyril; he will die in 869.

The new alphabet, attributed to Cyril but probably the work of his followers, will subsequently be revised to employ characters resembling those of the Greek to become the Cyrillic alphabet used in modern Slavic languages.

Basil, on Emperor Michael's orders, had divorced his wife Maria and married Eudokia Ingerina, Michael's favorite mistress, in around 865.

During an expedition against the Arabs, Basil had persuaded Michael III that his uncle Bardas covets the imperial throne, and subsequently murders Bardas on April 21, 866, with Michael's approva .

Basil now becomes the leading personality at court and is invested in the now vacant dignity of kaisar (caesar), before being crowned co-emperor on May 26, 866.

This promotion may have included Basil's adoption by Michael III, himself a much younger man.

It is commonly believed that Leo VI, Basil's successor and reputed son, is really the son of Michael.

Although Basil seems to have shared this belief (and hated Leo), the subsequent promotion of Basil to caesar and then co-emperor provides the child with a legitimate and Imperial parent and secures his succession to the imperial throne.

It is notable that when Leo is born on September 19, 866, Michael III celebrates the event with public chariot races, while he pointedly instructs Basil not to presume on his new position as junior emperor.

Boris sends embassies to Pope Nicholas and to Louis the German in 866; the Pope’s immediate response is to send a mission to Bulgaria.

Ya'qub next invades Bamian, …

…Balkh, …

…Badghis, and …

The Cretan Arabs, despite some imperial successes in the latter half of the 850s against the Emirate of Crete, in the early 860s resume their raids, attacking the Peloponnese, the Cyclades, and Athos.

The Caesar Bardas in 866 assembles another large-scale expeditionary force to subdue Crete, but his murder by Basil the Macedonian only two weeks after the fleet sets sail from the capital spells the end of the undertaking.

Emperor Louis, in his efforts to restore order in Italy as met with considerable success both against Italy's turbulent princes and against the Saracens who are ravaging southern Italy.

He routs these invaders, who have seized Bari, Taranto, and various other places in southern Italy, in 866, but cannot follow up his successes owing to the lack of a fleet.

King Ordoño I of Asturias dies in Oviedo in May 866, marking the end of his 16-year reign. He is succeeded by his eldest son, Alfonso III, who ascends the throne as King of Asturias.

Alfonso III will go on to strengthen the kingdom, expand its territory, and lay the foundations for the future Christian Reconquista, securing his legacy as one of the most important early rulers of Asturias.

Robert the Strong and the Defense of Neustria (865–866)

Robert the Strong, a powerful Frankish noble and military leader, emerges as one of the most effective defenders of West Francia against the Viking threat during the mid-9th century. His bold and inspiring leadership in Neustria proves crucial in checking the depredations of the Northmen, particularly along the Loire River, where Viking raids are frequent and devastating.

The Victory Over the Northmen (865) and Reward from Charles the Bald

• In 865, Robert the Strong leads Frankish forces to a great victory over the Northmen, halting their raids in the Loire Valley.
• As a reward for his military successes, Charles the Bald grants him full control over Neustria in early 866, essentially making him the Carolingian ruler of the region, with broad autonomy to defend it against Viking incursions.

The Battle of Brissarthe (September 866) and Robert’s Death

• Later that year, in September 866, Robert leads his forces against a Viking raiding party near Brissarthe, northwest of Angers.
• The Northmen, possibly led by the renowned Viking chieftain Hastein, fortify themselves inside a church.
• As the Franks attempt to dislodge them, the Vikings launch a fierce counterattack, and in the ensuing skirmish, Robert is killed.

Consequences of Robert the Strong’s Death

• His death is a major blow to West Francia, as he had been one of the few leaders capable of resisting Viking invasions.
• His legacy lives on through his descendants, particularly the Robertian dynasty, which will later rise to power in West Francia, culminating in Hugh Capet’s ascension as King of France in 987.
• The Viking threat in Neustria remains persistent, and the Franks will continue to struggle to maintain control over their river settlements.

Robert the Strong’s Lasting Impact

• His military campaigns in Neustria lay the foundation for later Frankish resistance against Viking invasions.
• The Robertian family solidifies its position as a dominant noble house, eventually replacing the Carolingians as the ruling dynasty of France.
• The need for decentralized military leadership to counter the Vikings contributes to the rise of feudalism, as regional lords take on greater military responsibilities.

Though Robert the Strong falls in battle, his descendants will shape the future of France, and his efforts against the Vikings pave the way for later victories that will reclaim West Francia from Norse domination.