Born "Francisco López Gascón" in Rágama de Arévalo, Salamanca, Carvajal was admitted to the University of Salamanca only to return home in disgrace after a series of public scandals. Disinherited, Carvajal enlisted in the Castilian infantry bound for Italy to fight in Charles V's wars. He was present as an "alférez" when the mutinous Imperial army stormed Rome in 1527. However, instead competing in the violent plunder for gold and valuables, Carvajal seized legal documents belonging to a ranking Roman notary and ransomed them for a small fortune.