Years before a dispute between Captain America and Iron Man had the entire Marvel Universe picking sides in 2005's Civil War event, Steve Rogers and Tony Stark had a falling out that Iron Man won handily. The fight took place across two issues in 1988 and only involved the two of them, but it was the beginning of an animosity that would last for decades. Unlike the 2005 comics crossover or its 2016 film adaptation, the roles of the two Avengers in this case were reversed, with Captain America fighting to bring Iron Man in for violating the law.
The quarrel between Captain America and Iron Man occurs in the midst of two of the most well-known stories involving each hero. At the time, Iron Man was caught up in his Amor Wars story arc, which sees him dealing with the theft of his designs by the Spymaster, who sells them to rival Justin Hammer. When Hammer uses Tony's designs to equip a number of villains, Stark is forced to hunt down each one and neutralize the armor. Meanwhile, Captain America's self-titled series was in the middle of the famous story arc The Captain. That story involves Steve Rogers giving up his Captain America moniker and shield while continuing to be a superhero known simply as the Captain.
The storylines first intersect in Iron Man #228 by David Michelinie, Mark D. Bright and Bob Layton. The story starts off with the two longtime friends on good terms, as Steve visits Tony to get a new shield he can use while acting as the Captain. After fulfilling this request, Tony prepares to go to the Vault prison for supervillains, where the guards are outfitted with an armor design he created. Cap deduces that Tony will likely try to go to the prison and reclaim his armor to prevent it from getting into the wrong hands. He warns Tony that the Vault and its guards are necessary and asks his friend not to follow through with his plan. When Iron Man and War Machine infiltrate the Vault, the Captain arrives on scene and tells Iron Man to stop. While Cap is helping an injured guard, Tony zaps him with an electrical charge and escapes.
The conflict reaches a conclusion in Captain America #341 by Mark Gruenwald and Kieron Dwyer. When Tony arrives home with a lady friend, Steve is waiting in his mansion. He says he's there to return the shield Tony gave him, inform him of the damage caused by his assault on the Vault, and take Iron Man to the authorities. Determined not to go down without a fight, Tony suits up and the two duke it out in his living room. Cap gets in a few hits, but Iron Man mostly evades him. The fight breaks out onto the lawn, where Iron Man hits the Captain with a high-density beam. Without a shield to deflect the blast, Steve is incapacitated long enough for Iron Man to get away again. He promises that the two will have a talk about ethics once he's accomplished his mission, and Steve decides to himself to give Tony a chance to restore his tarnished honor.
The two patch things up in Iron Man #238, but their relationship is never quite the same. After Iron Man electrocutes Cap in Iron Man #228, Michelinie writes in the narration, "No words are spoken; none are needed. For both men know that a bond has been broken today...a bond as old as their friendship...as deep as their innermost thoughts. A dear and precious link that may never be whole again." That certainly turns out to be true. Steve and Tony have butted heads numerous times over the years, and despite friendship and respect, there is always a simmering level of distrust between them. The roots of this distrust can be traced back to their very first Civil War, where Iron Man trounced Captain America.