The Carolingian dynasty, as the successors to Charles Martel are known, officially took control of the kingdoms of Austrasia and Neustria in a coup of 753 led by Pippin III (r. 752–768). A contemporary chronicle claims that Pippin sought, and gained, authority for this coup from Pope Stephen II (pope 752–757). Pippin's takeover was reinforced with propaganda that portrayed the Merovingians as inept or cruel rulers, exalted the accomplishments of Charles Martel, and circulated stories of the family's great piety. At the time of his death in 768, Pippin left his kingdom in the hands of his two sons, Charles (r. 768–814) and Carloman (r. 768–771). When Carloman died of natural causes, Charles blocked the succession of Carloman's young son and installed himself as the king of the united Austrasia and Neustria. Charles, more often known as Charles the Great or Charlemagne, embarked upon a programme of systematic expansion in 774 that unified a large portion of Europe, eventually controlling modern-day France, northern Italy, and Saxony. In the wars that lasted beyond 800, he rewarded allies with war booty and command over parcels of land. In 774, Charlemagne conquered the Lombards, which freed the papacy from the fear of Lombard conquest and marked the beginnings of the Papal States.[L]
When did Stephen II become pope? (If the question is unanswerable, say "unanswerable")
752