What is Johnny's first real contact with war? Do you think he was coward? Was Rab? Why or why not?

Johnny is never involved as infantry. He is largely a messenger. He would have seen violence but not been directly involved in assault or defence. Rab eventually does see action and is mortally wounded in the first volley. Neither are cowards. They both served in a way they thought they could help. Both risked their lives for their cause.