In the Doctor Who episodes Army of Ghosts and Doomsday, the Earth is put in jeopardy when the Cybermen from a parallel Earth infiltrate the Torchwood Institute headquarters in Canary Wharf, London. They are able to pass into our world via a dimensional rift created by Void sphere caught between universes, and after passing through, the sphere pushes all the way into our reality and then opens. Emerging from the Voidship are four Daleks known as the Cult of Skaro, who carry with them a Gallifreyan relic from the Time War that they call the Genesis Ark. Shortly after emerging from the sphere, the Cult become aware of the Cybermen invasion already in progress. The Cybermen propose that they and the Daleks join forces to conquer the universe, to which the Daleks respond by gunning down the Cyber troops. The Cyber-Leader warns the Daleks that they have declared war, to which Dalek Sec responds as merely being "pest control". The Doctor and his allies choose the lesser of two evils by helping the Cybermen break into the Daleks' chamber, but even with dozens of Torchwood troops and hundreds of Cybermen, the four Daleks shrug off the combined assault and retaliate in kind. Thus, the Battle of Canary Wharf begins.
During the fighting, Mickey Smith - one of the Doctor's allies - falls against the Genesis Ark. Having travelled through time before, his DNA awakens the Ark, which the Cult of Skaro open high in the sky over London. As it turns out, the Genesis Ark is a Time Lord prison ship containing millions of Daleks, which are all released and begin systematically slaughtering everyone on the streets below, human and Cyberman alike. During the conflict, the Cybermen conduct a rapid conversion drive, upgrading humans as quickly as they can using local materials rather than those they brought from their own world. But regardless of the Cybermen's numbers, the battle is completely one-sided as the Daleks' shielding protects them from all the Cyber's weapons. As the two mechanical armies fight, the Doctor works out a way to reverse the dimensional shift that allowed both armies to pass through the Void, sucking in everything saturated with Void particles. The plan succeeds and the Daleks and Cybermen are banished into the Void, all except for the members of the Cult of Skaro, who use an emergency temporal shift to leap through time and arrive in New York City during the Great Depression. With the invaders gone, the Doctor seals the rift between the parallel Earths so as to prevent any further damage to either universe. Unfortunately, his companion Rose Tyler was left stranded on the parallel Earth, unable to return.