Apart from a short time spent in the French resistance and as a prisoner during World War II, he served with the Foreign Legion from 1936 onwards.

His father was an active duty career officer and captain in the 42nd Infantry Regiment, killed in 1916 at the Marne, without seeing his family since the outbreak of World War I in August 1914.

In July 1948, learning that a foreign parachute battalion would be formed in French Algeria, he volunteered, undergoing training at Philippeville where he was brevetted as a legion paratrooper.

[1] On 7 October 1 BEP and other units at That Khe were tasked with recapturing Dong Khé, but were ambushed by superior Viet Minh forces.

By 7 October the French were trapped in the Coc Xa gorge, Jeanpierre divided the survivors into small groups and led 22 legionnaires back to That Khé, which had already been occupied by the Viet Minh and he and his men were captured.

[4] 1 REP conducted security operations against the FLN during the battle of Algiers, during which Jeanpierre was badly wounded by a grenade launched by Saadi Yacef.

[8] Shortly after, Captain Ysquierdo reported on the radio the following message: "Soleil est mort" meaning "the Sun (Jeanpierre) is dead".

In the annex of the report on the battle of the frontiers, 9 RCP commander Colonel Buchond stated:[11] "the work of a single Commandant assisted by only one Captain and who only in one day mounts four para combat operations each time mounting at least a dozen of para combat companies, assists to three briefings in three different places, ensures the air sortie of eight para air assaults, conducts three to four hours of flying in Alouette, moves his command post three times... this company Commandant is placed the 28th of April at 10:00 by helicopter only 200 meters from the rebels, demolishes an entire section, brings back three automatic arms, is found engaged at 18:00, embarked in vehicles at night, hits the road for four hours, is found at midnight at 20 km from there, engaged in combat till the morning, repacked at 08:00, is engaged again at 12:00 noon time after four hours truck drives, flown by helicopter at 15:00 and is found 20 km from combat engaging two companies of rebels..." The author André Maurois described Jeanpierre as: "Un héros au cœur généreux et au caractère détestable, une assez bonne combinaison pour un chef " (a hero with a generous heart and a detestable character, a fairly good combination for a chief).