Flux Offensive

The Flux Offensive was what Commander Stenck designated the Sontaran plot to exploit the Flux to secure "the final victory for Sontar".

The Sontarans occupied Earth for the second time since the beginning of the Flux, using human psychics to predict the origin point of the next Flux event. With that knowledge they lured the Dalek War Fleet and Cybermen forces to that location under the pretex of forming an alliance so they would fall victim to the Flux, intending to use Lupari vessels they'd seized to shield the Sontaran forces present from the same fate. (TV: The Vanquishers)

Prelude
The Division created the Flux to destroy space, whilst simultaneously liberating the Ravagers to attack structured time, as part of their plan to destroy the universe and move on to the next one. (TV: Survivors of the Flux) The Sontarans' Psychic Command foresaw its coming, (TV: War of the Sontarans) with Psychic Surveyor Kragar gleefully anticipating the greatest of conflicts in his report to Commander Ritskaw. (TV: The Halloween Apocalypse)

The Sontarans first attempted to capitalise on the Flux by invading Earth just as the Lupari, who were protecting humanity due to their species bond, shielded the planet from the Flux by surrounding it with a fleet of ships resistant to the Flux's effects. The Sontarns occupied Liverpool, using its docks to construct a fleet of timeships with which they intended to rewrite Earth's history to make it a Sontaran outpost throughout time, launching their first offensive into the Crimean War, creating an alternate timeline where they replaced Russia in the conflict. The Crimean offensive was forced to retreat by the Thirteenth Doctor whilst the 2021 occupation was undone by the Lupari Karvanista ramming a Sontaran timeship into the fleet, creating a temporal shockwave which removed the Sontarans from Earth entirely. (TV: War of the Sontarans)

Aftermath
The Daleks discovered the Doctor's role in the fate of the War Fleet and dispatched a squad of Executioner Daleks to exterminate her. Tracking energies of her TARDIS to ELF Storage on New Year's Eve 2021, the Executioners succeeded in killing the Doctor and her companions however they were resurrected when the TARDIS created a time loop. Despite the Daleks killing the Doctor numerous times, she managed to outwit them by luring them to explosives she'd setup and broke the loop by fleeing ELF Storage as they were destroyed. (TV: Eve of the Daleks)