Stephen II was a Roman elected to succeed Zachary in 752. His five-year pontificate transformed the relation of the papacy to the Western secular powers more decisively than any other in the early Middle Ages.
In 753 — facing a Lombard army at the gates of Rome — he became the first pope ever to cross the Alps, traveling in winter to Pippin the Short's palace at Ponthion in northern France. He prostrated himself in the snow before the new Carolingian king and obtained from him a solemn promise of armed defense and territorial restitution.
Stephen re-anointed Pippin and his sons (including the future Charlemagne) as kings at the Abbey of Saint-Denis on July 28, 754 — the foundational act of the Carolingian dynasty in its sacral character. He brought with him a written 'Donation of Pippin' by which the Frankish king pledged to return the disputed Italian territories (the Exarchate of Ravenna and the Pentapolis) to the See of Peter rather than to the Eastern Emperor — the foundational charter of the Papal States that would survive until 1870.
He returned to Rome in 754 with Frankish armies behind him; Pippin defeated the Lombards and presented the keys of twenty-two cities to Stephen on the altar of St. Peter. He died in Rome on April 26, 757.