A family relative of mine recently died and he was a World War 2 veteran. He was in the MP so I assumed he was at the rear doing stuff like checkpoints. However, he never liked talking about it at all. Which makes me wonder, did MP's serve on the front with the regular troops, and did they go to the concentration camps any? I wonder this because he was a real nice and caring person, and that tends to be the personality of those who had liberated the concentration camps and seen the horrors inside.
Depends on where he served, what unit he was in. If he was attached to a headquarters/supply section of an infantry unit or other combat unit then he may have well seen action. During the battle of the bugle MPs were caught up in the fighting. When the infantry would advance into occupied areas the MPs would mainly be charged with handling the POWs and refugees, but also the left behind enemy forces, holdouts, snipers, demo teams.