Their beliefs in freeing slaves has been inbeded in you and they are also your beliefs. You decide to join for the cause Upper and Lower Canada became a haven for run away slaves. Your father wants you to become a Dentist like he is. You want more adventure than that. You join the army for the great adventure of your life.
Many youth look for adventure and look at the army as a way to get it.
Part of your family immigrated to the States. You have a few cousins now fighting in the great war. You decide to join the army and fight with them. Immigration was easy then. It was a fully open border.