sherloques:

Captain America: The First Avenger Audio Commentary:

“This scene was added in [post-production] just to have him change his attitude and be determined. That was always the thing we were trying to balance. He gets activated by hearing about Bucky, that’s the thing that really makes him realize that it’s time to take a stand and contribute in a way that’s more than just doing the show. Bucky has got to be the only reason that he would go AWOL for. It becomes personal.”