When a self-centered youth's family is captured by an invading army, he trains as a knight before setting out to rescue them. As the kingdom teeters on the brink of collapse, the fate of both his family and kingdom depend upon a single decision. (Improved – hopefully)

Thanks for all the feedback and advice! I really appreciate it.

I like pacifist better than callous. In the context of war, its seems to me that callousness is an asset, not a liability. It might not make him a better person, but it makes him a better fighter.

Yes it's getting better!

I agree that "self centered" is not good - it's difficult to connect to the character.

What do you think of:
When the family of a pacific youth is captured by an invading army, he must take the oath of a knight in order to rescue them.?

In fact in a movie there is always an internal conflict (like overcome his nature) and an external conflict (beat the enemy) - I think you're supposed to put only the external conflict in the logline.