 A sergeant in the United States Army , Rogers ' best friend and member of his squad of commandos . Stan has signed on for " five or six pictures " . He revealed that he did not know anything about the comic books , but watched a lot of documentaries and films about World War II in preparation for the role , calling Band of Brothers " very helpful " . About the role , Stan stated , " Steve Rogers and Bucky are both orphans and kind of like brothers . They kind of grow up together and look after each other . It 's a very human , relatable thing ... I also wanted to look out for how their relationship changes once Steve Rogers becomes Captain America . There 's always a competition and they 're always one @-@ upping each other . I paid attention to how Bucky is affected by Steve 's change and suddenly Steve is this leader " . 
