a) 18 years old is not a child.
b) there were strong rules and safety procedures.
с) I actually meant USA.
Even today, there is a mandatory military service in some countries, do not know about Germany in particular, but in Switzerland, for example, they are all obliged to undergo military training. The same is for Israel.
And just to preanswer your possible question -- despite of mandatory military training in USSR, I wasn't in the army. I was declared unfit for combat due to medical issues (small weight/height ratio. I was what it is called 'nerd' nowadays, thin and weak).