During the Battle at the Triskelion, HYDRA operative Brock Rumlow was pinned under rubble after a Helicarrier crashed into the side of the building. Rumlow survived but gained severe facial scars and was subsequently hospitalized.
Several months later, after learning about the death of Alexander Pierce, Rumlow escaped from the hospital where he was staying. Recovering items from S.H.I.E.L.D.'s research and development labs, he set up an arms sale to draw HYDRA out of hiding.
Upon learning of their arrival, Rumlow opened fire on them as a way of telling their superiors he was no longer a member of HYDRA. Taking up the alias "Crossbones", Rumlow went on the run and aligned himself with several mercenaries, unaware that Captain America and the Avengers were trying to track him down.
Seeking to draw out the Avengers, Rumlow traveled to Lagos, Nigeria and planned to steal a biological weapon from the Institute for Infectious Diseases. However, Captain America became aware of the planned attack and informed the other Avengers. Upon arriving in Lagos, Scarlet Witch and Black Widow went undercover at a local cafe while Falcon positioned himself on a rooftop overlooking the city.
After noticing that a garbage truck was quickly approaching the IFID, Falcon deployed the Redwing only to realize that the truck was a battering ram.
By then, however, the "truck" had driven through the entrance and Rumlow's mercenaries had opened fire on several security guards. As poisonous gas slowly flooded the building, Rumlow quietly made his way to the third floor and found the bioweapon he was looking for.
The Avengers then converged on the building and proceeded to take out several of the mercenaries. Falcon used the Redwing to find and confirm Rumlow's location before informing Captain America.
Using her powers to lift Captain America onto the third floor, Scarlet Witch then focused on venting the gas out into the open air while the others proceeded to deal with the remaining mercenaries.
Captain America searched for Rumlow only to learn that he had already left. Black Widow managed to intercept Rumlow and tried to electrocute him only to learn he can no longer feel pain.
He then threw a grenade at her, but she used a dead mercenary's body to shield herself from the blast. Rumlow escaped, but not before entrusting the bioweapon to one of his men.
While Falcon, Scarlet Witch, and Black Widow set out to retrieve the bioweapon, Captain America confronted Rumlow and learned that the former STRIKE commander blamed him for his injuries.
Meanwhile, Black Widow managed to locate the bioweapon and confronted the mercenaries tasked with maintaining it. When they threatened to kill everyone in the surrounding area unless she surrendered, she reluctantly complied. The Redwing suddenly appeared and subdued them while Black Widow secured the bioweapon.
Captain America managed to subdue Rumlow and began pressing him for information as to the identity of the person who ordered him to obtain the bioweapon. Rumlow claimed Bucky Barnes was pulling the string before activating a suicide bomb attached to his vest, intending on taking Captain America with him.Scarlet Witch managed to contain the explosion around Rumlow and tried to move the blast away from innocent bystanders. However, she moved it too close to a nearby building and inadvertently destroyed it, killing twenty-six people, eleven of them being relief aid workers from Wakanda.
- "What legal authority does an enhanced individual like Wanda Maximoff have to operate in Nigeria?"
- ―News reports following the devastation in Lagos
With public opinion increasingly divided following the Battle of Sokovia, the destruction in Lagos was deemed a public relations disaster. Several international politicians, among them Wakanda's ruler King T'Chaka, called for the United Nations to create a system of accountability.
Secretary of State Thaddeus Ross brought the Avengers together and informed them that the United Nations was in the process of passing the Sokovia Accords, which would serve to monitor and police the increasing number of enhanced individuals.
The team became divided over the idea of oversight, with Captain America vehemently opposing it due to his mistrust of government agencies and Iron Man supporting it due to his guilt over the destruction of Sokovia.
Despite this, the United Nations arranged a formal ceremony at the Vienna International Centre in Austria. Among those in attendance were Black Widow, King T'Chaka and his son Crown Prince T'Challa. As King T'Chaka made the keynote address, a bomb detonated and resulted in the deaths of T'Chaka and several delegates.
In chronological order:
- Captain America: Civil War