Negroni was born in the Castle of San Colombano, also known as the Castello di San Colombano in Rogliano a commune in the Haute-Corse department of France on the island of Corsica. He joined the French Army when he was 18 years old. On 6 August 1870, he led the legendary charge of cuirassiers (mounted cavalry soldiers) in the second Battle of Reichshoffen (also known as "The Battle of Wörth") during the opening stages of the Franco Prussian War of 1870. Negroni was decorated on 20 August 1870 with Officer of the Legion of Honor.