Son of the Regiment (1981)

Summer 1943. A group of scouts from an artillery division stumbles upon a 12-year-old boy during a raid behind enemy lines. The scouts are shocked by his appearance - completely wild, dirty, ragged, angry and hungry - a real "wolf cub". The scouts take him with them and study that he has been wandering through the forests for about two years, feeding on what infections, and hiding all the time.

Unfortunately the movie Son of the Regiment is not yet available on HBO Max.