what does the loud soldier give him? why? why does he give it to henry?

Wilson lays his hand on Henry's shoulder and says that, with a trembling lip, that this will be his first and last battle. He just has a feeling about it. He gives Henry a packet of letters to send to his family and then, crying slightly, turns away.

I think he gives it to Henry because Henry seems the most grounded of all the younger soldiers. He is not big on bravado and is level headed. If someone is to survive in battle, Wilson thinks Henry will.