The fragile alliance between the Avengers is shattered in the third Captain America film, directed at a breathless pace by brothers Joe and Anthony Russo.
Opening with a flashback to 1991 that sets one major character on their self-destructive path, Civil War underscores its bombastic title by pitting former allies against each other in a series of dizzying showdowns that cleave apart the Marvel Comics universe.
Scriptwriters Christopher Markus and Stephen McFeely repeatedly inhabit the blurred lines between heroism and villainy, examining the moral conundrums faced by superpowered warriors who have pledged to protect the innocent from the righteous crossfire.
Alas, no one emerges unscathed from the melee and the deep psychological wounds inflicted in these bombastic 147 minutes suggest that this muscular chapter signals a bittersweet end for some characters while blatantly teeing up standalone spin-offs for Spider-Man and Black Panther.
"Victory at the expense of the innocent is no victory at all," solemnly intones King T'Chaka (John Kani) from the battle-scarred nation of Wakanda.
If that is true then Captain America: Civil War is a crushing defeat for everyone except thrill-seeking cinema audiences.
A year has passed since the events of Avengers: Age Of Ultron and the US Secretary of State Thaddeus Ross (William Hurt) insists on the introduction of legislation - The Sokovia Accords - to control the superheroes.
Tony Stark, aka Iron Man (Robert Downey Jr), reluctantly submits, telling his compatriots: "I'm doing what has to be done to stave off something worse."
Steve Rogers, aka Captain America (Chris Evans), who has always been a staunch patriot, refuses to sign, fearful of the consequences of the Avengers relinquishing their independence.
The gulf between Stark and Rogers forces the remaining Avengers to take sides.
Natasha Romanoff/Black Widow (Scarlett Johansson), James Rhodes/War Machine (Don Cheadle), Vision (Paul Bettany), Prince T'Challa/Black Panther (Chadwick Boseman), and Peter Parker/Spider-Man (Tom Holland) all stand shoulder to shoulder with Stark.
Meanwhile, Bucky Barnes/Winter Soldier (Sebastian Stan), Sam Wilson/Falcon (Anthony Mackie), Wanda Maximoff/Scarlet Witch (Elizabeth Olsen), Clint Barton/Hawkeye (Jeremy Renner) and Scott Lang/Ant-Man (Paul Rudd), pledge their allegiance to Rogers.
A battle royale between the two factions unfolds just as a diabolical new enemy, Baron Zemo (Daniel Bruhl), threatens mankind.
Captain America: Civil War could easily trim 20 minutes from its bloated running time without diminishing the impact of the special effects sequences or the pivotal plot twists.
The Russo brothers choreograph destruction on a grand scale, including an adrenaline-pumping motorcycle chase on the rubble-strewn streets of Berlin.
Evans and Downey Jr puff out their chests for supremacy in every lavish frame, while Johansson somersaults sexily between the feuding factions.
A protracted sequence involving Stark, a nerdy Peter Parker and Aunt May (Marisa Tomei) sows seeds of hope that next year's reboot, Spider-Man: Homecoming, might revitalise the webslinging vigilante with whip-smart humour.
Miracles might happen.