Year 622 (DCXXII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar, the 622nd year of the Common Era (CE) and Anno Domini (AD) designations, the 622nd year of the 1st millennium, the 22nd year of the 7th century, and the 3rd year of the 620s decade. The denomination 622 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. Events By place Byzantine Empire Byzantine–Sasanian War: Emperor Heraclius sails from Constantinople with an expeditionary force (probably 50,000 men), and starts a counter-offensive against the Persian Empire (his young son, Constantine III, is left behind as regent under the charge of Sergius I, patriarch of Constantinople, and patrician Bonus). He lands a few days later at the junction of Cilicia and Syria, near Alexandretta and ancient Issus. Battle of Issus: Heraclius defeats the Persian forces under Shahrbaraz in Cappadocia. He recaptures Anatolia, but returns to Constantinople to deal with the threat posed to his Balkan domains by the Avars, and puts the Byzantine army into winter quarters in Pontus. Asia The Western Turks conquer the Oxus valley and cooperate with Heraclius against Persia, taking Khorasan (modern Afghanistan). Central America March 28 – Tajoom Ukʼab Kʼahkʼ becomes the ruler of the Mayan city state of Calakmul in southern Mexico and reigns until 630. By topic Religion September 9 or June 17 – The Islamic prophet Muhammad, after being warned of a plot to assassinate him, secretly leaves his home in Mecca to make the Hijrah (emigrate) to Yathrib (later renamed by him Medina), along with his companion Abu Bakr. They take refuge in the Cave of Thawr south of Mecca for three days, departing on September 13 or June 21. September 20 or June 28 – Muhammad does not enter Yathrib directly, but stops at its outlying environs of Quba. He establishes the Quba Mosque here, the first mosque of Islam. On July 2 (or September 24) he makes his first visit to Yathrib for Friday prayers. October 4 or July 13 – After a fourteen days' stay in Quba, Muhammad finally moves from Quba to Yathrib, and is greeted cordially by its people. Here he drafts the Constitution of Medina, an agreement between the various Muslim, Jewish, Christian and pagan tribal communities in the city, forming