Attack on the Cathedral of Contemplation

During the Second Dalek War, the Dalek Supreme led an attack on the Cathedral of Contemplation in a bid to establish a bridge through time allowing the Daleks to attack Earth Central Command directly. They were resisted by the Fourth Doctor and the Tenth Doctor, in another multi-Doctor Event. (AUDIO: Out of Time)

Time travel strategies
The Second Dalek War had gone wrong for the Dalek Empire many times over. It had started after the failed attempt to set the Earth Empire and Draconian Empire at war with each other (TV: Frontier in Space) and the subsequent failure to awaken the 10,000-strong Dalek army on Spiridon. (TV; Planet of the Daleks) Even harassment by recruited Earth criminals, chief among them Abslom Daak, proved very costly, (COMIC: Abslom Daak... Dalek Killer, Star Tiger) culminating in the total collapse of Operation Genocide. (COMIC: Nemesis of the Daleks)

Despite all of this, the Earth forces were baffled by the Daleks' ability to bounce back to a position of strength over and over again. Partly as a result of humanity failing to organise a long-term united front alongside the Draconians, the Daleks held onto the initiative. (AUDIO: Out of Time) Nevertheless, the Daleks privately acknowledged that they were losing the war and came to consider time travel a viable alternative strategy, despite the areas in this field in which their knowledge and capabilities remained limited. (PROSE: Prisoner of the Daleks)

Entry into the Cathedral
The Daleks engaged a demoralised Earth unit on a planetoid in Sector 5, near the edge of Draconian space. One soldier, Private Jora, lost her resolve and fled to the Cathedral of Contemplation when a doorway opened. The rest of her unit, including her father, Captain Zenna, were all killed. The Daleks collected body-prints in order to create new duplicates.

Safe in the Cathedral, which existed outside of time, Jora met the Fourth Doctor, though revealed little about where she had come from. She also met with the Tenth Doctor, who accidentally crossed his own timeline after some unauthorised tampering with the Cathedral's temporal barriers.

Although the Daleks were unable to enter the Cathedral, they were able to send in a duplicate of Captain Zenna, who acted on the pretence that he was there to retrieve his daughter from her desertion. Secretly, he opened one of the doors, allowing the Daleks to enter via a time corridor with the Dalek Supreme, addressed as the Supreme Commander, leading Grey Daleks in the invasion. When the Abbess refused to surrender the Cathedral and its occupants to the Daleks, the Supreme murdered her on the spot. Unknown to the Supreme, the Abbess had a special connection with the Cathedral and without her, the whole place threatened to collapse within an hour.

Resistance was almost instantly overcome while the Doctors banded together to help all the pilgrims and refugees inside the Cathedral get to safety. Some of the Daleks were splashed and blinded with the Fourth Doctor's paint, while others were electrified and taken out in a trap set by the Tenth Doctor. One survivor of the latter trap was executed by the Supreme for failure. However, the Fourth Doctor was captured assisting Zenna, discovering too late that he was a duplicate. With his mission completed, Zenna fell into a directionless trance. The Daleks exterminated him as he had outlived his usefulness and they took the Doctor hostage. (AUDIO: Out of Time)

Bridge to Earth Central Command
The Supreme hooked the Doctor up to the Cathedral, intent on using his knowledge of time travel to pilot the Cathedral and its doorways and open up the time and place of the Daleks' choosing. Their ultimate goal was 26th century Earth, where they could attack Earth Central Command directly. With the Cathedral under their control, the Supreme declared the Daleks would "win this war and all wars".

The Tenth Doctor, after ensuring that Jora, the Abbess' apprentice Kivall and the others could make it safety out of the Cathedral, returned to rescue his past self. He willingly gave himself up to the Daleks so he could also be connected to the Cathedral as part of a plan to thwart the Daleks.

At the Doctor's suggestion, the Supreme had them pilot the Cathedral to a predetermined destination as a test. When the Supreme was satisfied that the right destination had been reached and that the Doctors would not be able to perform any further trickery, he ordered the doors to be opened on Earth ahead of the Dalek attack. The attack force was waiting on Skaro, ready to jump through the time corridor and the Cathedral directly to Earth. The Doctors mocked the Supreme for cowardice as he intended to stay inside the Cathedral while his subordinates did all the fighting.

The Daleks reached Earth but every one of them was wiped out in an instant. Although the Doctors had directed the Cathedral to Earth, as the Supreme had confirmed, they had done so in the year 5,000,000,000, not the 26th century, and the Dalek attack force fell victim to the expansion of the Sun at the moment of Earth Death. The Supreme and the Fourth Doctor then closed the doorway before the Sun's expansion fed back through the time corridor and engulfed Skaro as well, though the more bitter and vengeful Tenth Doctor thought the Daleks would have deserved such a fate.

Jora entered the area and shot the Supreme so the Doctors could escape, but the Dalek was only temporarily immobilised and gave chase. At the same time, the Cathedral's collapse began to accelerate. The Doctors and Jora fled through the doorway to meet up with the other refugees and closed it behind them to prevent the Supreme from escaping. He was killed as the Cathedral fell around him. (AUDIO: Out of Time)

Aftermath
The Supreme's successor continued to explore time travel as a means for the Daleks to win the war. In a secret facility on Arkheon, the Daleks sought to breach the Arkheon Threshold to enter the Time Vortex and alter human history from its very beginnings. The gambit proceeded until the Daleks encountered the Tenth Doctor yet again. After the loss of the Exterminator and the Battle of Arkheon, a time travel victory was effectively closed off to the Daleks. (PROSE: Prisoner of the Daleks) The war "fizzled out" in an "untidy conclusion" soon after. (PROSE: Deceit) Nevertheless, by the time of the Tenth Dalek Occupation, the Daleks had overcome many of their limitations. The Dalek Emperor eventually launched the Dalek forces into the Time Vortex, beginning the Last Great Time War. (PROSE: A Brief History of Time Lords)

As a result of crossing his own timeline, the Fourth Doctor forgot about these events after they had finished. He began to regain these memories in his tenth incarnation as the attack played out. The latter described the experience as a frustrating form of deja vu, in that he knew what was going to happen but only after it had happened. (AUDIO: Out of Time)