Those tactics were also a consequence of changes in German enlistment. After several years of war and heavy losses on the Eastern Front, the German army was forced to rely more heavily on enlisting teenage soldiers. Due to lack of training in more complex group tactics, and thanks to rifle training provided by the Hitlerjugend, those soldiers were often used as autonomous left-behind snipers. While an experienced sniper would take a few lethal shots and retreat to a safer position, those young boys, due both to a disregard for their own safety and to lack of tactical experience would frequently remain in a concealed position and fight until they ran out of ammunition or were killed or wounded. While this tactic generally ended in the demise of the sniper, giving rise to the nickname "Suicide Boys" that was given to those soldiers, this irrational behavior proved quite disruptive to the Allied forces' progress. After World War II, many elements of German sniper training and doctrine were copied by other countries.