Pietro d'Acquarone was born in Genoa, the son of Count Luigi Filippo d'Acquarone and his countess, born Maria Pignatelli Montecalvo. The boy embarked on an army career, joining a cavalry regiment and serving in Libya during 1913. In May 1915 the Italian government was persuaded by the British to enter the war against the Austrians: d'Acquarone served on the northern front. He won a bronze medal at Falzarego on 21 August 1915 and a silver medal at Monfalcone on 15 May 1916. After the war was over he was employed as military instructor to the crown prince. This meant a move to Rome and the start of a long professional association - increasingly complemented by close friendship - with the Italian royal family.