Lorencez was born in Paris to a minor noble family. His parents were Caroline Nicolette Oudinot de Reggio and Guillaume Latrille de Lorencez, a veteran of the French Revolutionary wars and the Napoleonic Wars, making the young Lorencez the grandson of
Marshal Oudinot. He studied at the
military academy of
Saint-Cyr, one of France’s most prestigious military schools, from 1830 to 1832, graduating as a third sous-lieutenant at age 18. He later became a captain in 1840 before he served first in
Algeria in charge of the 3e chasseurs à pied, specialized light infantry sent to handle skirmishes in the country's rough terrain. In 1845, his men were put under the command of lieutenant-colonel
Aimable Pélissier, a future marshal who operated at the time in the west of the town of Dahra controversially helping to kill Algerian combatants and civilians in the Dahra caves creating a scandal in France. Lorencez was then wounded and mentioned in several dispatches being distinguished notably at the Siege of Zaatcha in 1849 serving under colonel
Canrobert, another future French marshal, commanding the 1er battalion of Zouaves helping the decisive end of the bloody siege. He was then promoted to Lieutenant-Colonel commanding the 7e de Ligne at age 35. On his return to France, Lorencez was promoted to the rank of
colonel of the 49e de ligne in 1852, the year that
Napoleon III seized power and proclaimed himself emperor of the
Second French Empire, but Lorencez would be a staunch Bonapartist for most of his career. In 1855, at the
Battle of Malakoff during the
Crimean War, he commanded a brigade in 5th division of 2nd corps where they were pushed back in ferocious fighting against the Russians at the Bastion du Mat. However, the French managed to take Malakoff leading to the
fall of Sevastopol and the 41 year old general caught the eye of the emperor. Lorencez was sent back to France to recover, commanding French forces in stationary and peace command in France from 1855 to 1861 and inherited his recently deceased father’s estate and titles. ==French expedition to Mexico==