Kathleen Erskine is different; She was born with mutations that no one (at the time) would understand. After moving from Nazi occupied Germany to escape the wrath of HYDRA leader Schmidt, her and her father begin working with the US Army to construct a serum from Kathleen's mutations. Her father's original hopes for the serum were to advance medicine and create vaccines for multiple diseases, but instead he finds himself constructing a weapon. Injecting a being with this serum would enhance their nature, make them stronger, bigger, and better - An army of these super humans would be used to take out HYDRA, and ultimately win the war. The Colonel wanted an Army. He got Steve Rogers.