This paper evaluates the significance of emperor Heraclius Constantine III, the eldest son of Heraclius, for Byzantium in times of political and military crisis. The first part examines how Heraclius established his family as an imperial dynasty of Byzantium between 613 and 622. The second section analyzes how the young emperor represented his father in Constantinople, while Heraclius waged war against the Persian Sasanids during the 620s. The final segment deals on the one hand with the joint rule of Heraclius (...) and his eldest son after Byzantine victories against the Persians and, on the other hand, with the growing influence of Heraclonas. Finally, the contribution explores Heraclius Constantine’s III role as Augustus senior after his father’s death in 641. The until now often understudied emperor was thereby of essential importance for Byzantium’s stability in the first half of the 7th century. (shrink)