Captain America : The First Avenger
Physically, Steve Rogers (Chris Evans) is not sufficient to become a soldier. That's why he failed. Never give up, Steve and then register to be part of a military experiment known as Project: Rebirth. The purpose of this program is to create a super soldier who will be relegated to the battlefield.
With existing technology, the U.S. military later changed Steve Rogers into the super soldier named Captain America. Unfortunately, the government then consider this experiment has a cost too high and therefore not willing to have Captain America fell to the battlefield. Instead, Captain America and then used as a mascot to boost morale of the soldiers.