Guy Schlesser was born at Neuilly sur Seine in 1896.

In August 1914, aged 18, he volunteered to join the armed forces. He was admitted to the St Cyr Special Military School, after which he was posted to the infantry. In January 1916, while serving within the 238th RI (Infantry Regiment), he was promoted to second lieutenant. In August 1917, Lieutenant Schlesser, commander of a company of the 305th RI, was wounded at Mort-Homme. He was then transferred to the aviation where he served as observer within the 277 squadron. Aged 22 by the time the First World War ended, he had already received four commendations and had been made Knight of the Legion of Honour...

During the interval between the two world wars, Captain Schlesser was transferred to the Army staff, where he was appointed squadron commander. He thus served within the 11th armoured division after which he returned to EMA as intelligence officer.

In May 1940, Lieutenant-Colonel Schlesser was on mission to Belgium when the German launched their offensive. He took over the command of the 31st Motorized Dragoon regiment. He was wounded and taken prisoner at Saulieu on June 16, 1940. Having succeeded to escape, he passed through the free zone where he was made commander of the 18th Chasseurs, and later on of the 2nd Dragoons. In March 1941, Colonel Schlesser left France and went and joined the 5th Armoured Division. Thus, on November 17, 1944, he was at Héricourt, Haute-Saône, where he handed over the Lizaine bridges intact to the 2nd Moroccan DI before receiving, from the general commanding the 28th American DI, the honour of being the first to enter Colmar, liberated after very fierce confrontations. On April 14, 1945, Brigadier General Schlesser was appointed commander of the 5th DB, which he led right up to Danube, at the end of a triumphant ride.

The war had ended. In 1951, Major General Schlesser was appointed to command the 1st army corps and the area south of Germany occupied by French troops. By the time he was retiring from the army in 1956, he was promoted to the rank of lieutenant general.