How did Pepin strengthen the Frankish kingdom?

A:

Pope Stephen II asked Pepin, king of the Franks that lands now held by the Lombards be "restored" to the papacy, because four centuries earlier Constantine had granted them to his predecessor, Sylvester. This claim was based on a forgery that Stephen showed Pepin, now called the "Donation of Constantine." King Pepin accepted Stephen's Word that the document was genuine and ceded a great wedge of land along the Adriatic coast to Stephen. This in turn became known as the "Donation of Pepin" and according to traditional later accounts, Pepin personally laid the Donation of Pepin on the tomb of Saint Peter.

The Papal States created by this donation made the pope a feudal lord and gave real financial value to his office. While Pepin certainly helped the pope and his successors, he arguably did not help the Church, as the papacy became a prize for the great families of Rome and its neighbourhood, resulting in centuries of clerical infighting, corruption and open warfare.