Originally a governor (satrap) for the Seleucid Empire, Diodotus took advantage of the empire's wars in the west (against Ptolemaic Egypt) to declare independence around 250 BC. He proclaimed himself king, minting coins with his own image and adopting the title 'Soter' (Savior). This marked the beginning of the Greco-Bactrian Kingdom, which would last for over a century and expand further into India. He was succeeded by his son, Diodotus II.