(some say Castuera) in Extremadura, Spain around 1500 (some sources put his date of birth as early as 1497 or as late as 1505) to an impoverished hidalgo family. In 1520 a civil war broke out in Castile, the Revolt of the Comuneros, and Valdivia joined the army of Spanish king Charles I. He later fought in Flanders in 1521 and Italy between 1522 and 1527, participating in the battle of Pavia as part of the troops of the Marquis of Pescara. In May 1527, Valdivia was involved in the sack of Rome as a member of Charles I's mutinous mercenary army.