27th century Dalek invasion

The 27th century Dalek invasion was an attempted invasion of Earth waged by the Daleks led by the Golden Emperor in the first part of the 27th century. It followed a two hundred peace with the human race after which the Daleks were allowed to be rearmed following their defeat in a prior invasion. It was a far more minor attempt than the invasion in the 25th century and the initial declaration of war was more broadly addressed to "all the planets in every sky" rather than the Solar system specifically. (COMIC: The Mechanical Planet)

Origins
Towards the end of the 25th century Dalek invasion of the Solar system, the Daleks were forced to retreat to Skaro where they activated a force field to prevent the Space Army from landing. Eventually, Jeff Stone ordered that a gap in the force field at one of the poles be sealed. This threatened to suffocate the Daleks and after receiving a note telling them of this they soon lowered the field to discuss peace terms. (PROSE: Break-through) As part of the treaty, the Daleks promised to never leave Skaro again and end their dreams of conquest. (COMIC: Battle for the Moon) All Dalek weaponry became stored in a big space vault above Skaro and the Daleks themselves had their gunsticks removed. (COMIC: The Mechanical Planet) An Age of Universal Peace began in 2409. (PROSE: Break-through!)

In the early 27th century, after "two hundred years" of peace, an unknown Mechanical Planet moved through the universe destroying planets it came across, serving a potential threat to both Earth and Skaro. Earth possessed few weapons because of the many years of peace and did not understand how to use the Daleks'. The Emperor came to Earth and assured ambassador Brit Sovard that with their weapons returned to them they could deal with the planet. Brit reluctantly agreed and humans Jay and Gregg rode with the Emperor on his ship to ensure the success of the mission. After the planet was destroyed, the Emperor asked that the humans warn Earth and "all the planets in every sky" that the Daleks will come to conquer them. (COMIC: The Mechanical Planet)

Assassination of the Defence Minister
Soon after, the Daleks infiltrated Earth and came to be based beneath the yet to be finished Octagon building. They made Humanoid copies of several people in authority including Minister of Defence Tal Yorke, who they had kidnapped along with his family. The humanoid replaced the real Yorke for the Nine Planet Screen broadcast at which he was to make a different speech that would have damaged Earth's alliances. Before it begin, however, Yorke was seemingly assassinated by Agent Meric Scrivener of Unispace Security who then fled. He was pursued by Agent Arthur Lippert, Agent Brit, and journalist Tom Lytton. They followed him first to the burning remains of Yorke's mansion and then to the Octagon, believing him to be insane. Lytton found a switch inside and they continued where they discovered many prisoners manacled to the walls. They were quickly confronted by a Dalek who was shot and killed by the concealed Meric. He explained to the trio that he had known Yorke for a long time and knew the one at the conference to be a fake. He killed the fake and fled in case he was detained for questioning giving the Daleks time to relocate. Meric, Brit and Arthur freed the prisoners after Meric deduced Lytton to also be a humanoid. In his report, Lippert suggested that Meric be awarded the Nine Planet Star Decoration for his intelligence, endeavour and bravery, an idea Unispace Controller for Earth Bronson Bailey heavily endorsed. (PROSE: The Secret Struggle)

Reconnaissance and espionage
When Brit realised that Borg and Zemmer had commandeered her ship, the Daring with the intention of robbing the Dalek Treasure House on Skaro she protested because they were at war. They planned that the Daleks would blame Unispace Security for the theft which would escalate tensions. Brit managed to escape with her ship leaving the Daleks to exterminate Borg and Zemmer whom they thought were just pirates. (COMIC: Treasure of the Daleks)

In search of a five-leafed clover, Pat Kelly travelled to Skaro where he bluffed the Emperor into allowing him to stay in the Dalek City where he could look around. Upon meeting with the Emperor again, Kelly complimented him on their hydroponics chambers and made special note of their clovers. Reasoning that Kelly must be a spy and that he noted the clovers because he knew they would grow quickly, blocking their metal roadways and strangling their machines, he had Kelly's ship the Emerald Isle fitted with the clovers to bring certain doom to Earth. The Daleks allowed Kelly to leave and after hearing Kelly's seemingly happy reaction, the Emperor remarked that he was probably undergoing the last stages of insanity. (PROSE: The Five-Leaf Clover) After destroying a race of Birdmen who intended to conquer Earth after using Skaro as a testing ground for their invasion, the Emperor lamented that their secret of invisibility had died with them as it could have been a useful weapon against the humans. (COMIC: The Invisible Invaders)

On 16 October 2612, Captain Rod Marlow was ordered by Scrivener to make a sweepsurvey of Esmera in the 27th Galaxy as reports had been received that the Daleks had landed on the planet and built Interferer Beams to block all radio waves on Earth and the surrounding planets. Marlow discovered six incomplete Interferer machines but after another sweep of the planet returned to see them fully completed. However, he soon ran into difficulty and was forced to evacuate his damaged ship, the Gypsy Joe. After approaching the construction site, Marlow discovered an Orbitus that had been ordered to protect the Interferer Beams. After discovering rust and fearing damage, the Orbitus deconstructed and rebuilt the machines every day. Marlow reprogrammed the Orbitus to obey only human commands and ordered it to destroy the Interferer Beams. On 18 October, Marlow and the Orbitus returned to Earth for the former's son's birthday and the latter as a gift for him. (PROSE: The Log of the "Gypsy Joe") Space gangster Karsoff later commented that it was the only one outside of Skaro at the time. (COMIC: The Orbitus)

Historical discrepancies with the Dalek Wars
The 27th century invasion was separated by the 25th century invasion by "two centuries of peace", (COMIC: The Mechanical Planet) first declared in 2409, (PROSE: Break-through!) during which the Daleks were confined to Skaro (COMIC: Battle for the Moon) and comprehensively disarmed. (COMIC: The Mechanical Planet) This conflicted with accounts of the Second Dalek War fought through much of the 26th century, starting in 2540 (TV: Frontier in Space, PROSE: Love and War, et al.) until it "fizzled out" (PROSE: Deceit) circa the 2580s, (PROSE: Prisoner of the Daleks) though it was followed by "another Dalek War". (PROSE: Deceit)

The narrator of The Dalek Conquests noted that a precise chronological account of Dalek history was very tricky as the Daleks possessed means of time travel. He suggested the possibility that the Daleks involved in the Second Dalek War were not necessarily native to the 26th century. (AUDIO: The Dalek Conquest) During the Second Dalek War, the Daleks did possess technology theoretically capable of large-scale time manipulation. (PROSE: Prisoner of the Daleks) The exact effect this had on history, and on the ensuing 27th century invasion, is unclear, (AUDIO: The Dalek Conquest) although the Third Dalek War closely followed the era of the Second. (PROSE: The Chase) The Exxilon Gambit of the Third Dalek War (PROSE: The Secret Lives of Monsters) was said to have occurred in the 27th century. (PROSE: The Secret Lives of Monsters)

Reconciling the Dalek Wars
As highlighted above, the precise history of the related 25th and 27th century invasions depicted in The Dalek Book and The Dalek World is muddled by the later inclusion of the Second Dalek War of the 26th century into the mythos. These kinds of continuity snags stemming from contradictions with early 60s Dalek spin-off material are not uncommon, with the numerous versions of the Daleks' creation providing a more well-known example.

The Dalek Conquests tentatively suggests that the Daleks involved in the wars of the 26th century changed history as their time travel technology became more advanced. The Dalek Handbook goes slightly further, suggesting that the Daleks who "reckless[ly]" travelled back to the 26th century may have undergone the process of "overwriting their race's own timeline, restaging past battles, perhaps even exterminating their own earlier selves," or otherwise coexisting with previous Dalek generations (who would have been confined to Skaro).

The Third Dalek War, which is roughly indicated to have closely followed the Second, is dated by AHistory, A History of the Universe and The Dalek Handbook to c.2600. If both conflicts do take place in the same era, it may be that the 27th century invasion and the Third Dalek War are the same conflict, or merged as a result of time travel. Alternatively, the 27th century Dalek invasion may have been overwritten by the Third Dalek War through the means suggested by The Dalek Handbook.

These would not be the only examples of the Daleks changing the history of their own wars in this way. In Mission to the Unknown, it is established that the Daleks largely stayed in hiding in the run-up to the Great War in the 41st century, with The Dalek Outer Space Book depicting only relatively minor encounters with the SSS tasking place in the interim. However, The Only Good Dalek later depicted the post-Time War Daleks of the New Dalek Paradigm as having waged open war against humanity for much of since the 40th century.