21st century Dalek invasion

The 2009 Dalek invasion of Earth was a war fought between the New Dalek Empire and other races - mostly humans. It was fought in the Medusa Cascade in a pocket dimension that was put one second out of sync with the rest of the Universe in 2009.

Background
In the first year of the Last Great Time War, Davros's command ship flew into the jaws of the Nightmare Child at the Gates of Elysium. He was rescued by Dalek Caan, the last survivor of the Cult of Skaro. After activating an emergency temporal shift, Caan entered the timelocked Time War and rescued his creator, losing his mind and gaining psychic abilities by flying "into the wind and flame". (DW: The Stolen Earth)

Davros made Caan his prophet and set to work reviving the Dalek Empire of before the Time War. After building the Crucible, restoring the Dalek Fleet to two hundred ships and creating thousands of Daleks with the Kaled mutants inside grown from the cells of his own body, Davros set to work creating a reality bomb. This superweapon was to destroy all of reality in every universe except the Crucible, leaving Daleks the only species in existence. (DW: Journey's End)

To power the reality bomb, twenty-six planets and one moon were stolen from times and places across the universe so their gravitational fields, once aligned, would act as a gigantic engine. (DW: The Stolen Earth / Journey's End) These included Earth, which brought the problem to the Tenth Doctor's attention. The Shadow Proclamation, after the Doctor's visit to them, wanted to go to war with the as yet unknown perpetrators of this event. However, the Doctor did not wish for a full-scale war and left for the Medusa Cascade. (DW: The Stolen Earth)

Invasion of Earth
Not long after the planets were brought into the Cascade, the Dalek Fleet attacked. Most of the efforts seemed to go to Earth. The Unified Intelligence Taskforce and the armies of Earth fought back, but were no match for the Dalek onslaught and were quickly slaughtered. The Valiant was destroyed almost immediately, the British Prime Minister Aubrey Fairchild was killed, the RAF retreated over North Africa and military bases across the planet were attacked and personnel exterminated, although Martha Jones used Project Indigo to teleport away with an Osterhagen Key.

Other worlds out of the twenty-seven were inhabited. These would have presumably put up a resistance. These invasions were not shown.

A subwave network, created by the Mr Copper Foundation and developed by Harriet Jones, former British Prime Minister, was used by Harriet to try to contact the Doctor. While the Daleks attacked Harriet's house, killing her, Harriet, Torchwood, Martha and Sarah Jane Smith (with the help of Mr Smith) transmitted a message to the Doctor, helping him find the location of the stolen Earth. The Daleks, traced the signal and attacked Torchwood. (DW: The Stolen Earth)

The Doctor arrived as the Dalek assault continued. Thanks to a time lock in the Torchwood Hub, the Torchwood team survived the attack on them. Sarah Jane, trying to find the Doctor, was found by Daleks but saved by dimension-hopping Mickey Smith and Jackie Tyler. They surrendered to the Daleks to find the Doctor, who had been taken prisoner with Donna Noble, Jack Harkness and Rose Tyler and taken to the Crucible. (DW: Journey's End)

Reality Bomb
The Daleks, using Davros' plans, had created a weapon called the reality bomb. It would destroy everything, even parallel universes. It was powered by the twenty-seven planets the Daleks had stolen. They ran a test of the bomb on a small group of human prisoners, including Sarah Jane Smith, Mickey Smith and Jackie Tyler. Mickey and Sarah Jane escaped to a side chamber and Jackie teleported to it with her dimension jump just before the weapon was tested.

This saved them from being reduced to atoms. This terrible weapon would wipe out all life in every universe. In Pete's World, a universe which the Doctor said was further ahead in time than his, the reality bomb had already put out the stars. Meanwhile, the Daleks captured and tried to destroy the TARDIS with Donna Noble still inside. The regenerative energy in the Doctor's severed hand triggered a Meta-Crisis in conjunction with Donna Noble. A new version of the Tenth Doctor was produced. This Meta-Crisis Doctor and Donna escaped in the TARDIS, which everyone else thought destroyed in the Z-Neutrino core. They prepared to turn the reality bomb on the Daleks themselves.

Sarah Jane, Mickey, Jackie and Captain Jack threatened to detonate a warp star to destroy the Crucible if the Daleks did not back down and Martha Jones threatened to destroy the Earth with the Osterhagen Project to make the required twenty-seven planets twenty-six if the same thing wasn't done, but the Daleks teleported them all to the Vault and trapped them there with the Doctor and Rose. The Meta-Crisis Doctor and Donna arrived in the TARDIS to put their own plan into action, but were quickly stopped by Davros, who zapped them with his electricity-shooting prosthetic hand.

For a moment all seemed lost. However, the shock that Donna had received caused her Time Lord side to activate. She had become part-Time Lord when the Meta-Crisis Doctor was created, causing her to gain the Doctor's intelligence. She manually deactivated the reality bomb, disabled the Daleks and released the others by using controls with the "gut instinct" of a human and the intelligence of a Time Lord. (DW: Journey's End)

Destruction of the Crucible
With the reality bomb disabled and Dalek controls malfunctioning, the Doctor's companions got rid of all of the Daleks in the Crucible. Mickey held off Davros with Rose's gun. The two Doctors and Donna started returning all twenty-seven planets to where they belonged, but the Supreme Dalek descended to the Vault and attacked, disabling the machinery before Jack killed him. All of the planets but Earth had been returned, but the Doctor readied the TARDIS to tow it back. The Doctors also realised that Dalek Caan had been manipulating everything to lead to the end of the Daleks. With his warped mind no longer truly Dalek, he had realised how evil they were. Goaded by Dalek Caan and knowing the Daleks had sufficient numbers to take the universe by force without the reality bomb, the Meta-Crisis Doctor used the control panel to overload all of the Daleks' Dalekanium and blast it back, destroying the Daleks and their ships and blowing up the Crucible.

The two Doctors and their companions escaped in the TARDIS. Although the Doctor offered, Davros refused to come with them and presumably died when the Crucible blew up, along with Dalek Caan and all of the remaining Daleks. With the help of Mr Smith, K9, Ianto and Gwen, the Doctor towed the Earth back to where it belonged with Sarah Jane, Mickey, Rose, Martha and Jack acting as co-pilots in the TARDIS. (DW: Journey's End)

Aftermath and legacy
The effects of the reality bomb broke down the Void, releasing the Cybermen who had been locked away inside. (DW: Doomsday) They fell to Victorian era London around December 1851. They were later stopped by the Tenth Doctor, who sent them into the time vortex, where they disintegrated. (DW: The Next Doctor) In Pete's World, as the reality bomb was stopped, dimensional retroclosure restored the damage and sealed the Void again. (DW: Journey's End)

While the Doctor believed all the Daleks destroyed, one ship and three Daleks survived and escaped through time to 1941 Earth orbit with a progenitor device. They were eventually destroyed by the new, pure race of Daleks created by the progenitor due to their impurities. (DW: Victory of the Daleks)

Shortly after the invasion, by September 2009, at least half of Earth accepted the existence of alien life, while the other half were in denial. The events, combined with other invasions, led to an increase in suicide from crises of faith. (TW: Children of Earth: Day One)

Future historical figure Adelaide Brooke, commander of the first mission to colonise Mars in the 2050s, was a little girl at the time of the attack on Earth. Both her parents were lost and presumed killed. Her father's last words to her were to stay inside. She did, but a hovering Dalek approached her house. It saw Adelaide, but apparently realising she was a fixed point in time, did not exterminate her. According to the Tenth Doctor, Brooke's exploration of Mars, destined to end with her death, not only inspired generations of her family to reach beyond Earth, but also had a major impact on the human race leaving the confines of Earth. (DW: The Waters of Mars)

Despite the impact the invasion had on the people of Earth, the Eleventh Doctor discovered that his companion, Amy Pond, despite being from 2010, knew nothing of it. (DW: Victory of the Daleks) He later linked this to the nature of the time field, a form of crack or entity that could erase both people and events from history by unwriting their/its existence. When the cracks erased an event from history, the change to history was usually minor. In some cases, the consequences of the event still remained. (DW: Flesh and Stone) It is unclear whether the Doctor's restoration of the Universe with Big Bang Two (DW: The Big Bang) restored the memory of these events to the public at large, although at least one fixed point in time - Adelaide Brooke's exploration of Mars - was tied directly to her retaining memories of the invasion in the years following 2009.