I've never heard of this French movie until the British best selling author Antony Beever referred to it in an article 'The greatest war movie ever – and the ones I can't bear':
In my view, the greatest war movie ever made is The 317th Platoon, a French film from 1965 set during the country’s first Indochina war. This was the original “platoon movie”, whose format later directors followed but failed to match in its portrayal of characters and their interaction, to say nothing of the moral choices and the corruption of combat. It is followed closely by 1966’s The Battle of Algiers, set during the Algerian war of independence. This was one of the first war films to adopt a quasi-documentary approach, and tackle the moral quagmire of torture justified by the need to save lives.
Link:https://www.theguardian.com/film/201...s-i-cant-bear?

The director was Pierre Schoendoerffer, whose experiences of combat as a military cameraman and as a prisoner of war during the conflict in Indochina greatly affected him. He died in 2012. His obituary (the first underlined link above) has this passage:
One of the first films to deal with the subject, The 317th Platoon focused on the conflict between an inexperienced officer (Jacques Perrin) and a tough veteran of the second world war (Bruno Crémer) as the group struggle to survive in the jungle behind enemy lines. The difficult shoot, with a crew of six, in the middle of a Cambodian forest during the rainy season, added to the authenticity of the film, photographed realistically in splendid black and white by Coutard and soberly directed. "I imposed a strict military regime on everyone," Schoendoerffer recalled. "A war film shouldn't be made in comfort." The resulting film could have been seen as a harsh cautionary tale at the time when American involvement in Vietnam was escalating. Hollywood began to approach the war, seldom more effectively, some years later.
Link:https://www.theguardian.com/film/201...schoendoerffer

Alas the film is not on YouTube and appears to be on some websites after registration. It has some different reviews too. Most versions are in French and on blogger implies those with English sub-titles are very poor. and a short clip is on:http://alphahistory.com/vietnamwar/317th-platoon-1965/