Islam is an extremely limited moral system. In spite of the fact that world religions abound, most are somehow bound up in the worship of either God (Jove, Jehovah, or some other absolute creator deity) or of some person as God (Jesus, Alexander, Krishna, Ceasar or one of the Christian martyrs like Ignatius or Alban or someone like that). There are also ancestor cults and religions of virtue, although few people want to be in the company of someone who lives solely for martial courage, or to worship only a god of Justice (lawyers are very unpopular). No one likes the generous, they always seem to be giving away what belongs to someone else, usually YOU!
I think peace is a good thing to wish for, if not to outright pray for. Having said that, it's just not very aesthetic to attack someone ONLY for being in an army, someone like that might be primarily there out of a sense of duty, or to grow up with courage, or even because required by factors beyond his control.