Answer:
They were motivated to do so.
Step-by-step explanation:
I’m assuming this as WW2.
After WW1 every major country pretty much made a treaty which made germany suffer the most, their economy crippled and their place in the world was in dust. Hitler turned the German people’s anger at the treaty towards the jews. And this led them to be motivated to join the war. Including people and soldiers of Germany. Of course the ones who didn’t go when drafted essentially was threatened/coerced.