Emperor Heraclius is ready in 622 to…

Li Shimin defeats Liu Heita in spring 622, forcing him to flee to the Eastern Turks, but Liu Heita soon returns with Turkish reinforcements and kills Emperor Gaozu's nephew Li Daoxuan the Prince of Huaiyang in battle, again seizing former Xia territory, although by this point Li Shimin and Li Yuanji have also defeated Xu Yuanlang and reduced his territory to a few cities.

Meanwhile, an intense rivalry has developed between Li Jiancheng and Li Shimin, as, while Li Jiancheng has made some contributions toward Tang's reunification of China, Li Shimin has been the one defeating and capturing the major rivals Xue Rengao, Liu Wuzhou, Dou Jiande, and Wang Shichong, causing him to possess the greater reputation among the army.

Li Yuanji, who is also often relied on by Emperor Gaozu as a general, supports Li Jiancheng in this rivalry, and often pushes Li Jiancheng toward a more hardline position against Li Shimin, wanting to be crown prince when Li Jiancheng becomes emperor.

Li Jiancheng and Li Yuanji have better relations with Emperor Gaozu's favored young concubines than does Li Shimin (as their mother Duchess Dou had died before Tang's establishment), and those concubines help rehabilitate Li Jiancheng's standing before Emperor Gaozu, causing him to no longer consider making Li Shimin crown prince instead, as he had at one point considered.

By winter 622, Liu Heita poses the only remaining major threat against Tang rule.

At the suggestion of his staff members Wang Gui and Wei Zheng, who argue that Li Jiancheng needs some personal victories to establish his reputation, Li Jiancheng volunteers to command the army against Liu Heita.

Emperor Gaozu thus sends Li Jiancheng, assisted by Li Yuanji.

Liu's forced have become bogged down while attacking Tang's Wei Prefecture (in modern Handan, Hebei) around the new year 623.

Li Jiancheng and Li Yuanji engage him at Guantao (in modern Handan as well), crushing him.

Liu flees north toward the Eastern Turks, but is ambushed and captured by his own official Zhuge Dewei, who delivers him to Li Jiancheng.

Li Jiancheng executes Liu.

Around the same time, Xu is killed in flight.

Meanwhile, Lin Shihong the Emperor of Chu, who had one point controlled modern Jiangxi and Guangdong, has died, and his followers have scattered.

Heraclius sails from Constantinople with an expeditionary force (probably fifty thousand men) and starts a counteroffensive against the Persian Empire.

He leaves behind his young son, Constantine III, as regent under the charge of Sergius I, patriarch of Constantinople, and the patrician Bonus.

During Heraclius's absence on campaign for the next years, Bonus will act as the effective regent of the Empire.

When Heraclius goes “out into the lands of the themes” in 622, hereby undertaking a struggle of what will prove to be seven years' duration against the Persians, he utilizes the third of his sources of strength: religion.

Clad as a penitent and bearing a sacred image of the Virgin, Heraclius leaves Constantinople, as prayers rise from its many sanctuaries for victory over the Persian Zoroastrians, the recovery of the Cross, and the reconquest of Jerusalem.

He is, in effect, leading the first crusade.

The warfare that ensues is nothing less than a holy war: it is partly financed by the treasure placed by the church at the disposal of the state; the Emperor's soldiers call upon God to aid them as they charge into battle; and they take comfort in the miraculous image of Christ that precedes them in their line of march.

Indeed, in the ensuing hostilities, a pious poet will contrast the dancing girls in the Persian general's tent with the psalm singers in the Emperor's.

…an offer Khosrau II rejects with contempt, referring to himself as beloved by the gods and master of the world, to Heraclius as his abject and imbecilic slave, and to Christ as incapable of saving the empire.

Heraclius, mindful of the propagandistic value of Khosrow's arrogant response, makes it public.

Muhammad and Khadijah have produced two sons, both of whom had died young, and four daughters.

The house of 'Abd al-Muttalib of the Banu Hashim clan of the Quraish tribe comprises a form of nobility in Mecca, based upon their hereditary duty to act as stewards and caretakers of the pilgrims coming to the city to worship at the Kaabah.

Muhammad’s criticism of the polytheism of the Meccan religion angers the merchants of Mecca, who reap large profits from pilgrims visiting such ancient pagan sanctuaries as the Black Stone, probably of meteoric origin, and a shrine for the pagan deities of the Arabs, which have come to be occupied by some hundreds of idols.

The idols represent many different tribes and as a result Mecca has became a center of pilgrimage, and the Kaabah's environs are an inviolable sanctuary.

This pilgrimage traffic adds considerably to the wealth of the merchants of Mecca, which also benefits from its position astride the caravan routes from Yemen (Arabia Felix) up to the Mediterranean markets.

The Hashim clan to which Muhammad belongs becomes the target of a boycott by other Quraish, but the unpopular preacher is still protected by Abu Talib.

After Abu Talib’s death in 619, however, the new clan leader is unwilling to extend his protection to Muhammad, whose wife Khadijah dies around this time.

The Meccan elite now openly oppose him, harass his small group of dedicated followers, and plot to kill him.

Faced with this persecution and curtailed freedom to preach, Muhammad and about seventy followers decide to sever their ties of blood kinship in Mecca.

Muhammad and his followers, in what will come to be called the hegira, or hijra (an Arabic word meaning “breaking off relations”, “abandoning one's tribe”, or “migrating”), accept an invitation to move north to the oasis in 622 to settle the disputes that have paralyzed civil life there.

He renames this year "Year One" of the Anno Hegirae (AH).

He continues to preach and recite the words which Allah reveals to him.

It is these passages, together with the earlier revelations at Mecca, which will eventually be written down in the Arabic script by his followers and collected to become the Qur'an—the word (often transliterated as Koran).

Historians note that some contributors to Emperor Gaozu's establishment of Tang had been wrongly killed by him or killed based on little evidence of wrongdoing, including Liu Wenjing, in 619, on an accusation that he had engaged sorcerers; Emperor Gaozu's cousin Dugu Huai'en in 620, on an accusation of treason; Li Zhongwen the Duke of Zhenxiang, in 620, on the accusation of collaboration with Eastern Tujue; and Liu Shirang the Duke of Yingyang, in 623, on the accusation of collaboration with Eastern Tujue.

The Tuyuhun and Tanguts regularly raid Chinese settlements along the western Tang frontier.

In 623, the Tuyuhun depart from their homeland in the pastures surrounding Qinghai Lake, known in Mongolian as Kokonur, and invade Gansu.

The Tang general Chai Shao is dispatched to defeat the nomads and prevent further incursions.

The Tuyuhun hold the higher ground and shoot arrows against the encroaching Tang forces.

Chai Shao devises a decoy by sending two dancing girls and a group of musicians to a small hill near the Tuyuhun camp.

The musicians play the pipa, a stringed instrument of foreign origin, while the girls position themselves on top of a hill.

On the hill, the dancing girls perform an erotic dance in front of the nomads.

The attention of the nomads is diverted entirely towards the girls.

The Tuyuhun soldiers break out of their military formation and rush to the hill for a clearer view of the dance.

Seizing the opportunity, Chai Shao surprises the soldiers who are distracted by the performance, and attacks them in the rear with his cavalry.

Over five hundred Tuyuhun soldiers are killed in the ensuing battle, forcing the Tuyuhun's retreat from Gansu.

Hostilities between the Tuyuhun and Tang continued after the battle.

China is by this point completely unified by the Tang dynasty except for the domain of Liang Shidu the Emperor of Liang, who controls modern northern Shaanxi and western Inner Mongolia, although, with Li Fuwei at Chang'an, Fu Gongshi rebels in 623 and declares himself the Emperor of Song.

Fu's rebellion, however, will be quelled by Li Xiaogong in 624.

Western Slavic tribes known as the Wends (known also as Sorbs or Lusatians), discontented with Avar domination, call on a Frankish merchant named Samo, who aids their revolt and, from his center, perhaps in southern Moravia (near Mikulcice or Devin), begins to forge several Slavic tribes into an independent political force, becoming their king around 623, his demesne stretching from the upper Elbe to the Danube.