Valentine succeeds Eugene II to the papacy in 827 but dies thirty or forty days after after taking office.

Gregory IV, chosen to succeed Valentine in December 827, had recognized the supremacy of the Frankish emperor in the most unequivocal manner, but papal dependence on the Roman Emperor has loosened through the quarrels of Louis and his sons.

In the sons' rebellion against their father, Gregory supports Lothair, hoping his intervention would promote peace, but in practice this action annoys the Frankish bishops.

Gregory's response is to insist upon the primacy of St. Peter's successor, the papacy being superior to the Emperor.