Pope Stephen II (III) dies. Because the papacy was under severe pressure from the Lombards and Byzantine emperors, Pope Stephen II tried to counter their power by allying himself with the only people he could turn to: the Franks, led by Pepin the short, Mayor of the Palace of the Kingdom of the Franks and father of Charlemagne.
In exchange for recognizing Pepin as King of the Franks Pope Stephen would receive military and political protection. Thus Pepin became not only king but also "Protector of the Church" and proceeded to invade northern Italy to end the Lombard threat to Rome.
He didn't succeed in eliminating the Lombards entirely and they will continue to be a major force on the Italian peninsula for several hundred years. Pepin did, however, relieve the pressure being put on Rome. Pepin turned a number of territories over to the control of the papacy, now known as the Donation of Pepin.