The title sounds more important than he is, but he accepts it anyway, because someone has to take care of the life-saving armour they wear. Protecting the protection – now that makes him sound much better, because they’re an army focused on defense rather than offense.
On the other hand, it also means it gets a little boring around camp, because there’s a lot of waiting around and nervous looks being passed from man to soldier, and really, they’re all children trying desperately to believe it’s still just a game where losing isn’t a permanent condition.
So when his master takes him along on their first offensive mission, he’s actually excited, not because he’s treating the whole war as a game, but because he’s always wondered what it would be like to follow someone to anywhere, knowing that he had your back and you had his. He can finally be a part of this absolute trust he’s sought for a long time, so he follows, and finds more than he imagined.