Iconoclasm has been given full rein under Theophilos.

To weaken the political influence of Greek Orthodox monasticism, the Emperor and his former teacher John "the Grammarian", now patriarch of Constantinople as John VII, have mounted a persecution against the users of icons in Orthodox liturgy and devotion.

Support for Iconoclasm soon wanes, however, and the vast majority of the Greek Christians rally to the defense of their sacred art.

The cultural revival stimulated by Theophilos includes two significant advances in the area of classical studies: the gradual substitution of the minuscule, or smaller, cursive hand for the uncial, or larger, script, and the increase in the number of scriptoria, or copyists' workshops.

Theophilos has also restored the University of Constantinople after its eighth-century decline and appointed the brilliant teacher Leo the Mathematician as its new rector.

In the aftermath of the sack of Amorium, Theophilos had sought the aid of other powers against the Abbasid threat: embassies had been sent to both the western emperor Louis the Pious and to the court of Abd ar-Rahman II, Emir of Córdoba.

The imperial envoys had been received with honors, but no help has materialized.

The Abbasids, however, have not followed up on their success.

Warfare will continued between the two empires with raids and counter-raids for several years, but after a few imperial successes, a truce and prisoner exchange—which excludes the high-ranking captives from Amorium—is agreed in 841.

The Cretan Saracens have attacked Euboea between 835 and 840, Lesbos in 837, and the coasts of the Thracesian Theme, whose governor (strategos), Constantine Kontomytes, inflicts a severe defeat on the Cretan Saracens in 841 when they raid the rich monastic community of Mount Latros.

Shortly before or soon after, Constantine's daughter marries the magistros Bardas, who is the nephew of Empress Theodora on his mother's side and of Patriarch John VII the Grammarian on his father's.

Bardas will later assume his father-in-law's surname.

The late Emperor Theophilos had in 837 raised Bardas, brother of the Empress Theodora, to the rank of patrikios and sent him together with the general Theophobos in a campaign against the Abasgians, but the imperial force had been defeated.

With the death of Theophilos, and the ascension of the two-year-old Michael III, a regency council had been set up, headed by Theodora.

Bardas and his brother Petronas, as well as their relative Sergios Niketiates, are also members, but it is the logothete Theoktistos who had quickly established himself as Theodora's chief advisor.

Bardas had still played an active role in the early days of the regency, encouraging Theodora to abandon Iconoclasm for good and taking part in the investigations that led to the deposition of the pro-iconoclast patriarch John the Grammarian and the restoration of the veneration of icons in 843.

In 844, however, Theoktistos blames Bardas for the desertions that had led to the Empire’s defeat in the Battle of Mauropotamos against the Abbasids, even though the logothete himself had led the imperial army, and has him exiled from Constantinople.

Following Bardas's exile and the death of Sergios, Theoktistos rules supreme alongside Theodora.

The imperial government, headed by the Empress-regent Theodora and the logothetes Theoktistos, have embarked on a sustained assault on the Empire's main political and ideological foe, the Abbasid Caliphate and its dependencies, following the restoration of the veneration of icons in March 843.

This aggressive stance is on the one hand facilitated by the internal stability that the end of the Iconoclasm controversy has brought, and on the other encouraged by a desire to vindicate the new policy through military victories against the Muslims.

The first such campaign, an attempted reconquest of the Emirate of Crete led by Theoktistos in person, had made initial gains, but ultimately ended in disaster.

After scoring a victory over the Arabs in Crete, Theoktistos had learned of a rumor that Theodora intended to name a new emperor, possibly her brother Bardas.

Theoktistos had hurried back to Constantinople, where he discovered that the rumor was false, but in his absence, the imperial army in Crete had been slaughtered by the Arabs.

Theoktistos, according to Byzantine sources, learns in 844 of an Arab invasion of imperial territory in Asia Minor, led by a certain 'Amr, probably the semiautonomous emir of Malatya, Umar al-Aqta.

The Arab sources do not make explicit mention of this campaign.

The Russian scholar Alexander Vasiliev, however, identified it with an expedition recorded in the poems of Abu Tammam and Buhturi, which was led by general Abu Sa'id and took place during the regency of Theodora.

Umar al-Aqta's participation is likely, as he often aided the Abbasids in their raids against the imperial forces.

According to Arab accounts, the troops led by Abu Sa'id comprised men from the border emirates of Qaliqala (Erzurum) and Tarsus.

The Arab forces united at Ardandun (possibly the border fort of Rhodandos) before raiding through the imperial themes of Cappadocia, Anatolikon, Boukellarion, and Opsikion.

Sa'id's troops sacked Dorylaion and even reached the shore of the Bosporus.

Theoktistos leads the imperial army in against the invaders, but is heavily defeated at Mauropotamos ("Black River").

The location of the latter, if indeed it is a river and not a simple toponym, is disputed; it was most likely a tributary of the Sangarius in Bithynia or of the Halys in Cappadocia.

Not only do the Greeks suffer heavy casualties, but many senior officials defect to the Arabs.

Theoktistos returns to Constantinople.

The Abbasids are unable to exploit their success due to the internal instability of the Caliphate.

Likewise, the Empire prefers to focus its strength against the ongoing conquest of Sicily by the Aghlabids.

Thus, an imperial embassy is sent to Samarra in 845, which is warmly received.

The Abbasids reciprocate with an embassy to Constantinople, where the two states agree on a truce and a prisoner exchange, which is held at the river Lamos on September, 16, 845.

A winter raid by the Arab governor of Tarsus shortly after the prisoner exchange fails disastrously, after which the frontier between Caliphate and Empire will remain quiet for six years.

Bardas has quickly become the moving spirit in the new regime.

A university is organized in Constantinople.

Ignatios, who had supported Theodora, is arrested and imprisoned in 858, and upon refusing to resign his office is deposed.

On December 25, Michael elevates to the patriarchate a layman, Photius, after the latter’s receipt of the lesser orders in six days.

Photius, a relative of the Patriarchs Tarasios and John VII Grammatikos, had after completing his own education begun to teach grammar, rhetoric, divinity and philosophy.

Following the marriage of his brother Sergios to Irene, a sister of Theodora, and Theodora’s assumption of the regency, Photius had become a captain of the guard and subsequently chief imperial secretary.

At an uncertain date, Photius had participated in an embassy to the Arabs.