Captain America: Civil War is the second film in Phase Three of Marvel Cinematic Universe.
The New Avengers, having enlisted Ant-Man within their ranks, tail Bucky Barnes, who has become a man without any identity, who in hopes of starting a new life is traveling to Wakanda, to organize a rendezvous with HYDRA. The New Avengers confidentially tail Barnes, however, their cover is blown up, and a mishap begins in Wakanda. Falcon and War Machine knock down Barnes and takes him back to US, while the rest of the Avengers attempt to prohibit Crossbones, (who is exploited to be an apparent leader of HYDRA) who is hellbent on bombing the Royal Palace. Ant-Man is stunned to see building sized HYDRA mercenaries, and he realizes that the Pym Particles that had been burglarized in the Cross Industries building, was reverse engineered for enhanced HYDRA soldiers. Lang reverses the Pym Particles and becomes Goliath-sized and defeats the other HYDRA mercenaries. Scarlet Witch levitates Crossbones up to the air, in order to prevent any bomb from defusing, however, Baron Zemo, now revealed to be the topmost leader of HYDRA, detonates the bomb, and the Royal Palace is blown up, killing king, T'Chaka. Baron Zemo and HYDRA escape. The Avengers are suppressed to escape.
This international incident involving Captain America and the Avengers results in collateral damage, prompting politicians to form a system of accountability and a governing body to determine when to call in the Avengers, as idealized by the secretive Tony Stark, which results in the fracturing of the team. Steve revives Barnes's memory, and they two ally again, before the Vision and War Machine betray the New Avengers and join Stark, who register in the Project Insight's classified operative, the Illuminati.
Baron Zemo strikes again, and the Avengers are not given permission to take care of the situation, however, Steve disobeys the government and attacks HYDRA along with the New Avengers. Baron Zemo escapes again, but now kidnapping Wanda Maximoff. Stark revolts against Rogers, who discovers Stark's intentions to dismantle the Avengers and create the Illuminati, a fail safe program which monitors A;; SUPER
- Project Insight is a classified operative designed by Tony Stark; and processed by S.H.I.E.L.D; Stark who is bent on creating an invulnerable galactic defense of his planet, is convinced that he can control and monitor all the superhuman activities within the planet, and he persuades Nick Fury to create this operative that consists of many people that will help form the confidential organization; the Illuminati, that Stark wants to be the most superior superhuman group in the world that will statistically monitor all the threats in the Earth. Stark recommended the Superhuman Registration Act in order to fracture the Avengers, in order to create the Illuminati and finalize Project Insight, so that they will enlist and provide help and support, by Stark`s way, and his command, and by his orders. After Steve uses the aid of Peter Parker to hack into Stark`s files, and when he learns of this, he realizes that Stark is also enlisting criminals and former fugitives for his own gains, and he learns that Stark is gradually becoming a menace to practically, everyone. In Captain America: The Winter Soldier, the Project Insight plan was discovered by many HYDRA soldiers, acting as S.H.I.E.L.D agents, such as Brock Rumlow and the S.T.R.I.K.E squadron, and after the plan was learned by HYDRA, they corrupted it, and used bombs in order to destroy the members of Project Insight, including Tony Stark and Stephen Strange with Bruce Banner and more, however, HYDRA`S plans were later foiled by Cap.
- William Stryker (played by Martin Freeman) is an American general, with the intent of experimenting and having trials with mutants (who he thinks is a genocide) and in order to confidentially run the Weapon X project in minimum profile while gaining the trust of the whole of America, he is elected as the National Spokesman and Director of Superhuman Activity Within US Borders.
- Peter Parker (Spider-Man) who is a new crimefighter, thinks that the Superhuman Civil War will cause grave dangers to the public, which will eventually make them more hostile of superheroes and superhumans all around the world, albeit the fact that the Civil War may corrupt many different identities, sources, and organizations. He participates in the Civil War, and Tony Stark, alias, Iron Man, faciliates him with an Iron-Spider suit, and convinces him that Captain America is the real enemy. However, when he learns that Stark is hiring burglars and former fugitives in his alliance, he rebels against him, sabotages his Iron-Spider suit, and joins the side of Captain America, which he knows is the righteous one, however in the process, his aunt who is involved in the war by the intent of Stark gets wounded by the Black Panther. In rage and turmoil, he quits from the war, and becomes neutral, and as T'Challa realizes what a mistake he has committed, he becomes neutral as well.
- The Results of the Final Battle only involved Stark against Steve in a collision course. Before the final battle, the other vital players were either left deceased (Falcon; succumbing to his injuries), or some quit (Spidey, Black Panther, Black Widow, Hawkeye, Scarlet Witch) or some were left defeated (Agent 13, War Machine, Vision, Ant-Man) because of multiple reasons. However, in this penultimate showdown, Captain America brawls against Stark in his Bleeding Edge Armor. It is a battle to the death, however, Captain America makes Iron Man`s armor sentient on itself, and it prompts the armor to self destruct, leaving Tony at the point of near fatality, but Cap even having the advantage to kill Stark, does not do so, as he shakes hands with him, and they decide, that Stark will win the battle for good, while Steve will retire and will get out of all contacts with Stark, SHIELD, or any of their other affiliations. Steve leaves everyone`s sight, Stark is healed, and he decides to scrap the Illuminati Initiative. Natasha and Clint go on the hunt for Banner, Peter Parker gets an algorithm from an unknown source, revealed to be Nick Fury, Vision and Wanda Maximoff reconcile, Falcon`s death is avenged as he has his own memorial center; Barnes becomes the new Captain America, Scott Lang consults with Hank Pym and they two search for the HYDRA members who stole some formulas of the Pym Particles, as shown in their own solo film. Black Panther returns to Wakanda and becomes it's finest warrior. Rhodes retires as War Machine and joins the military again as a post general, Agent 13 is consulted by Nick Fury who wants to settle a task with Peter Parker. Helmut Zemo dies, with his wish complete; the Avengers fractured. The heroes of the world are now solo, and that is why, Daredevil, Jessica Jones, Luke Cage and Iron Fist decide to assemble together as the Defenders of New York.