WARNING: The following contains spoilers for Marvel's Black Widow, playing in theaters and on Disney+ Premier Access.
First mentioned in 2012's The Avengers, the so-called Budapest Operation has achieved legendary status within the Marvel Cinematic Universe, connecting Natasha Romanoff and Clinton Barton through a shared experience. Alluded to across three films -- by the two heroes, and by Loki and Alexander Pierce -- the details of the mission have remained a mystery, until Black Widow.
Set in the immediate aftermath of Captain America: Civil War, the spy thriller forces Scarlett Johansson's Natasha Romanoff to confront the darkest parts of her past, including what really happened in Budapest. Although Black Widow and Hawkeye may remember the incident very differently, she nevertheless has a stark recollection of events, which continue to haunt her.
Following an attack by Taskmaster, Natasha abandons her hideout in Norway and heads for her former apartment in Budapest, where she finds both her "sister," Yelena Belova (Florence Pugh), and lingering damage from Hawkeye's arrow assault years earlier. ("Agent Barton was sent to kill me," Black Widow told Loki in The Avengers. "He made a different call.")
Although it's a little tricky to square Hawkeye's original assignment to kill Natasha with what she characterizes as the final step in her defection to S.H.I.E.L.D., the outcome remains the same: As relayed through flashbacks, and through Natasha's comments to Yelena, she and Clint Barton were tasked by S.H.I.E.L.D. with assassinating General Dreykov (Ray Winstone), the head of Russia's Black Widow Program.
When they located his target, however, he wasn't alone. Natasha used Dreykov's young daughter, first referenced by Loki in The Avengers, to lead her to the general's location. Natasha then ordered the detonation of the explosives within the building, fully aware the child was inside. "Dreykov's daughter was collateral damage," she explains to Yelena. "I needed her to be sure."
However, that wasn't the end of the Budapest Operation. Natasha and Clint then had to fight Hungarian Special Forces as they desperately sought an escape. "It took 10 days in hiding before we could even get out of Budapest," she recalled. As she and Yelena flee Taskmaster, they're forced to hide in the duct work of a Budapest subway station, the same place Natasha and Clint concealed themselves for two days.
But while the mission was deemed a success at the time, secured Black Widow's position within S.H.I.E.L.D. and cemented her bond with Hawkeye, it's ultimately revealed to have been a failure. Although Natasha was confident that Dreykov died in the attack, she learns from Yelena that he survived and, as the mastermind of the Red Room, remains a threat, to them and to the world.
Further, the fallout from Natasha's decision to carry out the mission with little regard for the fate of Dreykov's innocent daughter, Antonia -- to add more red to her ledger -- echoes throughout the years, to at least the time of Black Widow.
Directed by Cate Shortland, Black Widow stars Scarlett Johansson as Natasha Romanoff/Black Widow, Florence Pugh as Yelena Belova, David Harbour as Alexei Shostakov/Red Guardian, O-T Fagbenle as Mason and Rachel Weisz as Melina Vostokoff, with William Hurt as Secretary of State Thaddeus Ross and Ray Winstone as General Dreykov. The film is playing in theaters and on Disney+ Premier Access.