Kukai arrives back in Japan in 806 as the eighth Patriarch of Esoteric Buddhism, having learnt Sanskrit and its Siddham script, studied Indian Buddhism, as well as having studied the arts of Chinese calligraphy and poetry, all with recognized masters.

He also arrives with a large number of texts, many of which are new to Japan and are esoteric in character, as well as several texts on the Sanskrit language and the Siddham script.

In Kukai's absence, however, Emperor Kammu had died and has been replaced by Emperor Heizei, who exhibits no great enthusiasm for Buddhism.

Kukai's return from China is eclipsed by Saicho, the founder of the Tendai school, who finds favor with the court during this time.

Saicho has already had esoteric rites officially recognized by the court as an integral part of Tendai, and has already performed the abhisheka, or initiatory ritual, for the court by the time Kūkai returns to Japan.

With Emperor Kammu's death, Saicho's fortunes had begun to wane.

Isa ibn Mahan, who had been an early follower of the Abbasids, had mutinied after the Abbasid Revolution and was executed by Abu Muslim.

Isa’s son Ali had first appeared first in the reign of al-Mahdi (775–785) as commander of the caliphal guard (haras) and secretary of the army department (diwan al-jund), and had continued in these offices under al-Hadi (r. 785–786), having in addition the powerful post of chamberlain (hajib).

Under Harun al-Rashid, he had continued to serve as commander of the guard until 796, when he was named governor of Khurasan.

As a leader of the abna′ al-dawla, the troops that form the core of the Abbasid army in Iraq, he has antagonized the Khurasanis and oppressed them through heavy taxation, with the revenue diverted for the upkeep of the abna′ and for filling his own coffers; during his tenure, Ali has amassed a vast fortune.

Harun al-Rashid personally investigates complaints against Ali, whose ruthless exploitation of the province and oppressive fiscal measures has caused much resentment among the local elites.

Hearing of no wrongdoing and being showered with gifts, the caliph confirms Mahan in his office and departs for Baghdad.

The governor of Samarkand, Rafi ibn al-Layth, the grandson of the last Umayyad governor of Khurasan, Nasr ibn Sayyar,immediately organizes a revolt against the governor, defeating Mahan’s troops in Transoxania in 806.

Ali flees the province and the caliph, requesting an end to the revolt, pledges a new government sympathetic to the rebels’ demands, but fighting continues.

The revolt spreads quickly across Khurasan, finding support both among the Arabs and the Iranian natives.

Rafi also secures the support of the Oghuz and Karluk Turks.

Charles, bringing the Wends under his control in 806, has a fortress built to guard the valuable salt springs at Halle ("saltworks"), located on the Saale River in the region of the present German state of Saxony-Anhalt.

The churchman Nikephoros was born in Constantinople as the son of Theodore and Eudokia, of a strictly orthodox family, which had suffered from the earlier Iconoclasm.

His father Theodore, one of the secretaries of Emperor Constantine V Kopronymos, had been scourged and banished to Nicaea for his zealous support of Iconodules, and the son has inherited the religious convictions of the father.

Nevertheless, he had entered the service of the Empire, become cabinet secretary, and under Irene had taken part in the synod of 787 as imperial commissioner.

He then withdrew to one of the cloisters that he had founded on the eastern shore of the Bosporus, until he was appointed director of the largest home for the destitute in Constantinople around 802.

After the death of the Patriarch Tarasios, although still a layman, Nikephoros is chosen patriarch by the wish of the emperor Nikephoros (Easter, April 12, 806).

The uncanonical choice meets with opposition from the strictly clerical party of the Stoudites, and this opposition intensifies into an open break when Nikephoros, in other respects a very rigid moralist, shows himself compliant to the will of the emperor by reinstating the excommunicated priest Joseph.

Harun responds to the empire’s raids with a massive invasion in 806, leading an army with more than one hundred and thirty-five thousand men across Anatolia's Taurus Mountains and seizing the city of Heraclea Cybistra (Eregli).

The Muslims score victories on land and sea, taking …

…Tyana and …

…Ancyra in 806.

Nikephoros, unable to counter the Muslim numbers, agrees to make peace on condition of paying fifty thousand nomismata immediately and a yearly tribute of thirty thousand nomismata.

Nikephoros I and Charles I had tried to settle their imperial boundaries in 803.

A first treaty had indeed been prepared and sent to the East by Charles, who had started talks with Empress Irene.

The text, however, was never ratified by Nikephoros, as the Royal Frankish Annals, and Charles in a surviving document, explicitly state.

The Franks had already subdued the March of Istria, and after overturning the Avar khaganate, they claimed the rich Pannonian plain and the Dalmatian coast; following these events, Dalmatian Croatia, located in what is nominally Roman Dalmatia, had peacefully accepted limited Frankish overlordship.

Charles from 806 wages a generally successful war against Constantinople for control of the northern Adriatic sea regions of Dalmatia and Venetia.

The Muslim Arabs ravage Rhodes and Cyprus during the Abbasid invasion of 806.

Nikephoros consistently refuses to recognize Charles’s imperial title, but envoys of the East and West have made agreements over the possession of disputed Italian territory, namely, the provinces of Venetia and Dalmatian Croatia, during the first decade of the ninth century.

These seem to have been advantageous to the Venetians and to have guaranteed Constantinople’s sovereignty over them.