Bucky Barnes, another man out of time, is the new Captain America now...but today he's trapped in the past, because today is Bucky Barnes' birthday. See Bucky's favorite and least favorite birthdays - from the cold winters of the Depression on military bases, to the front lines of WW2 fighting alongside the Invaders, to his new mission as Cap. Oh yeah, and someone's trying to kill him. By Ed Brubaker and Luke Ross.
Bucky is attacked by some well-equipped opponents and he does not even know why. He bemoans the fact that this fight happens on his birthday but then remembers that most of his birthdays went the same way.
1941: On his 16th birthday, Bucky gets into a bar brawl and is put into confinement by his superiors. He has been a troublemaker for two years now and his majors is not sure what to do. He decides to put him into special combat training. Thereby he becomes Cap's partner.
1943, Poland: The invaders plan a surprise birthday party for Bucky because he turns 18. He catches their plans and the Human Torch says he mentioned Bucky's name to their matron. Soon they are attacked by Master Man and Warrior Woman.
Bucky finds out that the attackers are from a right-wing militant group called the Watchdogs who actually admired Cap.
1945, London: Cap and Bucky interrogate a German spy to find out what Baron Zemo is doing in England. Steve tells him that he spend his 20th birthday getting the Super Soldier serum. The same year they attack Zemo's castle and Bucky is captured by the Russians and turned into the Winter Soldier. As the Winter Soldier, there were no birthdays.
He defeats the attackers and destroys their weapons after they tell him the reason for their attack was him being the new Captain America. He goes back to the Avengers hideout where all the Avengers stage a surprise party for him.
Backup: Sentinel of Liberty - A recap of Captain America's comic history.