In Nazi Germany, no one was exempt from Hitler. If you were able bodied, it did not matter of what age, you had no choice but to join in Hitler's action.
You had a choice, but the choice they gave you, was you are either one of us, or you support them. If you do not join us, then you are of no use to Gemany. You are not seen as a good German.
If there was any hint of suspicion that you were not fully 100% in support of Hitler, then you and your family are in "not welcomed" in Germany. That means that you are an enemy and we all know how Hitler and his army treated people he thought were enemies.