By 1944 Germany was on the defensive and needed every man that was available. General conscription had been introduced in 1935, at which time it was a fairly accomodating system that allowed people some flexibility in when they did their service, but towards the end of the war this became "all hands on deck".
After Germany changed from the offensive to the defensive in 1943, it became possible and necessary to transfer an increasing number of Air Force and naval personnel to the Army, to enforce "voluntary" enlistment into the Waffen-SS and to commit line-of-communication units to regular combat not only against partisans but against regular enemy forces.
The increasing heavy losses of the Russian campaign forced Hitler to cancel his order exempting "last sons" of decimated families and fathers of large families from front line combat duty. Prisons and concentration camps were combed for men who could be used in penal combat units with the inducement of possible reinstatement of their civil rights.
Although a "total moblization" was carried out in the spring of 1943, after Stalingrad, it became necessary by the end of the year to lower the physical classification standards drastically and register men up to 60 years of age for military service. Even men with severe stomach ailments were drafted into special-diet battalions. During the summer of 1944, civilian occupations were reduced to an absolutely necessary minimum. Finally, the remaining male civilians from 16 to 60 were made liable for home defense combat service in the "Volkssturm" and even Hitler Youth boys and girls were called up as auxiliaries.
The German Draft