Year 628 (DCXXVIII) was a leap year starting on Friday (link will display the full calendar) of the Julian calendar. The denomination 628 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 Spring – Byzantine–Sassanid War: Emperor Heraclius issues an ultimatum for peace to King Khosrow II, but he refuses his generous terms. The war-weary Persians revolt against Khosrow's regime at Ctesiphon, and install his son Kavadh II on the throne on February 25. He puts his father to death and begins negotiations with Heraclius. Kavadh is forced to return all the territories conquered during the war. The Persians must give up all of the trophies they have captured, including the relic of the True Cross. Evidently there is also a large financial indemnity. Having accepted a peace agreement on his own terms, Heraclius returns in triumph to Constantinople. Third Perso-Turkic War: The Western Göktürks, under their leader Tong Yabghu Qaghan, plunder Tbilisi (modern Georgia). The Persian defenders are executed or mutilated; Tong Yabghu appoints governors (tuduns) to manage various tribes under his overlordship. Britain Battle of Cirencester: King Penda of Mercia defeats the West Saxons at Cirencester (southwest England), in what later will be Gloucestershire. After reaching an agreement, he takes control of the Severn Valley and the minor kingdom of the Hwicce. Central America February 5 – K'ak' Chan Yopaat, who had been the ruler of the Mayan city state of Copán in Honduras, dies after a 49 year reign that began in 578. February 21 – Chan Imix K'awiil, becomes the new ruler of the Mayan city state of Copán in Honduras, and rules until his death 67 years later in 695. Persia February 25 – Khosrow II, the last great shah of the Sasanian Empire, is overthrown by his son Kavad II. September 6 – Ardashir III, age 7, succeeds his father Kavad II as the twenty-fourth shah of the Sasanian Empire on the latter's death from the plague that is devastating western Persia. Arabia Muhammad, Islamic prophet, leads about 1,400 men on a pilgrimage to Mecca, where their passage is blocked. The Quraysh tribe and the Muslim community in Medina sign a 10-year truce (Treaty of Hudaybiyyah). By topic Arts and sciences Indian astronomer Brahmagupta writes the Brāhmasphuṭasiddhānta, an early, yet very advanced,