The Iron Ceiling
Happy Sam Sawyer accompanies the Howling Commandos during Peggy's mission to Russia. He is introduced as one of Peggy's former wartime comrades and immediately participates in the group's banter when the SSR agents recognize the Commandos. Sawyer humorously objects to the name "Howling Commandos," although Junior Juniper reveals that he was responsible for creating it.
Sawyer participates in the infiltration of the Leviathan facility and survives the operation with only a moment of having been held hostage and a bullet in the leg. His history with Peggy seems to give more longstanding credibility among the soldiers who actually fought alongside her, contrasting with the skepticism she continues to encounter inside the SSR.