The storyline consists of an eponymous seven-issue limited series, written by Mark Millar and penciled by Steve McNiven, and various tie-in books.

"[1] Civil War explores the conflict between freedom and security against a backdrop of real-life events and discussions, such as the U.S. government's increased surveillance of its citizens.

The Superhero Registration Act introduced in Civil War requires any United States resident with superhuman abilities to register with the federal government as a "human weapon of mass destruction".

One advocates registration as a responsible obligation, and the other opposes it, arguing the act violates civil liberties and the protection secret identities provide.

[5]Marvel announced in August 2006 that some issues of the main Civil War series would be pushed back several months to accommodate artist Steve McNiven.

Furthermore, various tie-in books, including the Civil War: Front Line miniseries, were delayed to avoid spoiling plot developments.

[8] After the publication of Civil War #7, Mark Millar described the book to Newsarama as "a story where a guy wrapped in the American flag is in chains as the people swap freedom for security".

[9] The New Warriors (Night Thrasher, Namorita, Speedball, and Microbe) battle a group of villains (Cobalt Man, Speedfreek, Coldheart, and Nitro) in Stamford, Connecticut, while filming a reality television show.

This team includes Hercules, Falcon, Danny Rand (who is acting as Daredevil in Matt Murdock's place),[13] Luke Cage, and the Young Avengers.

However, when a young member of the Yancy Street Gang is killed in the ensuing violence, Grimm, disgusted with both sides, leaves the country for France.

As the battle turns against them, a new weapon is brought into play: Project Lightning, a cyborg clone of Thor (created from a few strands of the Asgardian's hair and empowered by a technological copy of Mjolnir).

Bill Foster's death shakes up both sides: Stature and Nighthawk surrender and register, while the Human Torch and Invisible Woman oppose the act.

He explains Iron Man's decision to employ infamous mass murderers motivated the gun-wielding vigilante to come out of hiding, but also notes superhero registration has caused a huge drop in crime.

As the Punisher makes his way through the Baxter Building to retrieve plans for the Negative Zone prison, Sue Richards travels to Atlantis to persuade Namor to join the Secret Avengers, although he refuses.

As the final battle begins, Cloak teleports the combatants to New York City, where Namor and an Atlantean army arrive to fight alongside the Secret Avengers.

Cyclops thought it was preposterous for Professor X to appoint himself the representative of mutantkind, and his opposition to Xavier's proposal led Jean Grey to break up with him and marry Wolverine.

His team consists of Penance (Robbie Baldwin), Iron Spider (Natasha Romanoff), Captain Marvel (Carol Danvers), and the Thor clone known as Thunderstrike.

Steve Rogers (no longer called Captain America) and his teammates have been arrested and buy time off their sentence by performing suicide missions as the Thunderbolts.

Steve's team consists of Spider-Man (Peter Parker), Invisible Woman, the Punisher, and Bill Foster's Goliath (who survived the Civil War in this reality).

The remaining five heroes from the Mighty Avengers and Thunderbolts stay behind on Battleworld with the Sentry and fight villains attempting to gather the Iso-Sphere as the Civil Warriors.

The Civil War was avoided entirely in this reality due to her marriage to Steve Rogers, by deterring each other's more aggressive behaviour and allowing Reed Richards to complete the Super Hero Registration Program.

[21] In a reality where all the characters age naturally after Peter Parker becomes Spider-Man in 1962, the Superhuman Registration Act was passed shortly after the September 11 attacks in 2001 and lasted for years.

When Peter refuses Stark's offer to register, he is attacked by the U.S. Avengers (consisting of Tony Stark/Iron Man, James Rhodes/War Machine, Carol Danvers/Captain Marvel, Natasha Romanoff/Black Widow, Jennifer Walters/She-Hulk, and Danny Rand/Iron Fist all wearing power armors) before he is assisted by the Anti-Registration Avengers (consisting of Steve Rogers/Captain America, Clint Barton/Hawkeye, Luke Cage, Tyrone Johnson/Cloak and Tandy Bowen/Dagger).

After Tony is revealed to be a hologram and disappears, Spider-Man joins the Anti-Registration Avengers to follow his daughter's advice on leaving the world a better place for future generations.

[24] In What If Civil War Ended Differently?, a stranger appears in front of Iron Man, who is visiting Captain America's grave at Arlington National Cemetery.

[28] Unlike the previous story and the film, the conflict in this storyline is not about issues of government registration; instead, a new Inhuman, Ulysses, emerges with the ability to see predictions about the future.

The movie version of Civil War also differs from the comic substantially, former U.S Army General Thaddeus Ross as the U.S Secretary of State is involved in the registration debacle instead of S.H.I.E.L.D and Maria Hill as the former was dismantled in Captain America: The Winter Soldier and the latter's whereabouts are unknown at that point or is presumably in hiding with Nick Fury, with the fate of Bucky Barnes becoming a key element of the war after he is framed for the assassination of the Black Panther's father, the king of Wakanda.

Black Widow goes on the run after betraying Stark's side to help Rogers find the instigator of their fight, and War Machine is left crippled after injuries sustained in the final battle.

Later in the 2018 film Avengers: Infinity War it was revealed that Hawkeye and Ant-Man made deals with Ross to be placed on house arrest, so they could be with their families.

The impact of the Civil War is also heavily felt throughout the film as the Avengers' disunity and Rogers and Stark still being on bad terms, left them vulnerable to Thanos' invasion and the Blip.