[Him having heard of the Nazis makes this easier in some ways, he doesn't have to impress on him the severity of what they're dealing with. But it also makes it harder in others, more personal.]

HYDRA were the deep science division of the Nazi Party, human experimentation, weapons, that sort of thing. When the war ended they pretended to die out, but they just went underground, spread, grew. Pierce was the head of HYDRA where we come from.