In 610 Herakleios, son of the exarch of Carthage, deposed Phokas and initiated a century of rule by the Herakleian dynasty (see Dynasties of Empire section). Herakleios largely inherited the problems that had plagued Phokas’s reign: in the East, the Persians under Chosroes II began a new offensive, while the Avars and Slavs continued their incursions in the North, and elements within the empire, such as the leaders of Antioch still loyal to Phokas (or his memory) and general Komentiolos in Ankyra, resisted Herakleios’ new rule.
Early in Herkleios's reign the Persians scored a remarkable series of successes taking Antioch, Byzantine Syria, and Cilicia before moving into Palestine. In 614 Jerusalem fell, was sacked, and the True Cross was taken to Persia. Egypt was captured in 616 when Alexandria surrendered after a year–long siege. By 617 there was even a Persian army encamped across the Bosphorus from Constantinople. At the height of the Persian advance Herakleios considered returning to Africa and ruling the remainder of his empire from Carthage. Herakleios remained in the East, and in 622 personally began a counter attack through Armenia that forced the Persians out of Anatolia. When the Persians and the Avars united for an attack on Constantinople in 626, the Avars proved unable to assault the walls of the city and their attempts to ship Persian troops over to aid in the siege were frustrated by the Byzantine navy. In 627 Herakleios suddenly marched deep into Mesopotamia, leaving many of the Persian troops far behind on the front lines. At Nineveh he defeated the Persian army, killing the Persian general in single combat, and began ravaging the Persian heartland. Chosroes II was forced to flee from his palace as Herakleios advanced, and was eventually killed by his own people. The overthrow of Chosroes was followed by the speedy restoration of the prewar borders, the adoption of Christianity by Chosroes's successor, and the return of the True Cross to Jerusalem. Herakleios's triumph was short lived. In 636 his forces were defeated by the Arabs at the Battle of Yarmuk. This event marked the beginning of the Arab conquest of the Byzantine Near East which had extended as far as Syria and Palestine by the year of Herakleios's death.
In an attempt to heal the rift between Chalcedonianism and Monophysitism Herakleios proposed his policies of Monoergetism and, after the former’s ban in the Ekthesis of 638, Monotheletism. Both attempts were unsuccessful and their only result was to create yet more divisions within the Christian community in the face of the new religion, Islam. The displacement of elites to the capital after the loss of their cities completed a movement, beginning in the fourth century, toward the favor of privileged connections with the imperial court over local power structures. In addition, the removal of the eastern armies into the inner territories, and their resettlement there, initiated a new form of provincial administration eventually called the theme, first for the military units, and later for the geographical circumscription. It is difficult not to feel sorry for Herakleios, who lived just long enough to see his life's work disintegrate, being by then too old and unwell to do anything about it, a shadow of the man who had saved his empire just over a decade earlier.
Herakleios’s seals are notable for the depiction of his co-emperors (his two sons Herakleios Constantine and Heraklonas), and for the way in which both father and sons can be seen to age in their portraits. Herakleios’s beard and mustache grow, and Herakleios Constantine and Heraklonas, though initially youths much shorter than their father, become taller as the years progress. This was the first time that co-emperors had been associated on seals since the fifth century, and association would become a characteristic of both seals and coins until the end of the eleventh century. No seals in the Dumbarton Oaks collection were issued in the names of Herakelios Constantine, Heraklonas, or Martina (in the absence of Herakleios) during the period between the death of Herakleios and the ascension to the throne of his grandson Constans II in September 641. For a full cross-section of Heraklieos's seals and those of his family, see the Herakleian Dynasty in the Dynasties of Empire section of this exhibition.