Sovogda was a city in Russia that was targeted by Elena Derevko and Arvin Sloane to construct a massive Mueller device in to activate "Rambaldi's endgame". It resulted in an infection that transformed thousands of citizens into raged monsters, and left the rest of the population dead at their hands.
The APO team watched news reports of the riots and violence in Sovogda before realising what had happened. One of the news reports caught glimpses of the bottom edge of a large red ball that APO identified as a Mueller device. They deduced that it was part of Elena and Sloane's plan to activate the "endgame" of Milo Rambaldi. The Russian government refused to comment on the disaster. Moments later, a hacker friend of Marshall's from Moscow sent him footage of the streets of the city, where people were going wild (Search And Rescue).
To deactivate the Mueller device, the team had to find Irina Derevko, who they recently learnt was still alive. Sydney and Nadia found her and Irina agreed to help stop it. Around the same time, the CIA got word that the Russian government was planning to drop a nuclear device over the city to stop the supposed "disease" spreading. APO sent their team in four hours before the device was going to go off (Search And Rescue).
The DSR sent a team into Sovogda but the CIA lost contact with them (Search And Rescue). When APO landed, they waited in a street to meet with the team. When they found them, only an arm with the DSR transponder on was left. The rest of the team was presumed dead. They stumbled upon one of the team members - Brodien - whom Sydney recognised from her time with the CIA. He told them more about the infection. They were being watched by a member of Elena Derevko's team, who informed her of their arrival. Sloane offered to go and stop them (Before The Flood).
The APO team went into the subway to reach the epicentre of the Mueller device. Brodien was killed by one of the infected. They reached the epicentre, and were contacted by Marshall and Weiss who said that Elena was trying to uplink a subaudible frequency to the Russian mil-sat network to distribute the infection world-wide. The second that the bombers were scheduled to destroy Sovogda, the frequency would be broadcast causing the effects of Sovogda to occur worldwide. Weiss told them that they had around forty minutes to stop Elena. Marshall sent them building blueprints, and the team went in with the assistance of Sloane. They managed to destroy the device and Sovogda was flooded with water from the Mueller device (Before The Flood).
The strike on Sovogda was cancelled and the Russian government killed all those left infected in the city (Before The Flood).