The Daleks are a race of cyborgs originating on the planet Skaro and are the mutated remnants of a humanoid race known as the Kaleds. The Daleks consist of an external, highly durable robotic shell and an organic creature inside. The Dalek creature evolves (or mutates) over the course of their history, and is sometimes capable of independent movement and action away from the shell (at least for a limited period) and at others is immobile within the shell and totally reliant on it for survival.
The Daleks are active in several distinct timeframes in the course of the Doctor Who fictional continuity, and at various points command a vast empire spanning hundreds of planets in multiple galaxies, a single city on their home planet, and indeed at one point were reduced to a single Dalek which barely survived and managed to recreate the species using Kaled genetic material. The Daleks evolve during the course of the fictional history of the TV series, with early-history Daleks being relatively slow, ungainly and vulnerable to explosives and missiles. Far future Daleks hailing from the post-201st Century are capable of flight, time travel, limited teleportation and possess personal defence forcefields.
The Daleks are held to be the most dangerous lifeform in the Doctor Who fictional canon, and at one point are believed to have succeeded in destroying all other life in the universe. The Time Lords of Gallifrey averted this fate by sending an unwilling agent, the Doctor, to the moment of their creation to destroy them. Although he failed, he did retard their development and inadvertently ensured the survival of their creator, Davros, which later led to both a massive schism and civil war amongst the Dalek civilisation and a full-scale 'Time War' between the Daleks and Time Lords which led to the mutual and near-complete destruction of both species.
(note that this is my interpretation of the history of the race as given in Doctor Who based on the Daleks' changing levels of technology in the original and new series)
The Kaleds were originally a humanoid species native to the planet Skaro, the twelfth world of its star. The Kaleds developed a technologically-advanced civilisation before becoming embroiled in a nuclear war with another race called the Thals (it is unclear if the Kaleds and Thals were genetically different species or merely different national or ethnic groups of the same race). During the long years of the war, which also involved the use of chemical and biological weapons, much of Skaro was reduced to a wasteland and much of its indigenous animal life was killed off or mutated. A brilliant Kaled scientist named Davros experimented on mutations of actual Kaleds. Publicly, he claimed his experiments were designed to ensure the future survival of their species in a life-support/travel machine even if the planet became too radioactive to support their continued existence. In private, he experimented on the mutants, removing such 'weak' concepts as fear, pity, empathy and tolerance of other races and beliefs, and turned the supposedly innocent travel machine into a war machine equipped with sophisticated weaponry. When the Kaled government, horrified at Davros' experiments, tried to shut him down, Davros leaked intelligence to the Thals that allowed them to destroy the last Kaled city before he released his prototype Daleks into the Thal city, wiping out most of the population. The Daleks turned on Davros and apparently exterminated him. However, the intervention of the Time Lord known as the Doctor apparently changed history so that Davros survived (the Doctor, under the threat of torture and death, revealed details of the future history of the Dalek race, including their extreme capability for duplicity and ruthlessness, to Davros, who apparently took precautions to ensure his survival) and the prototype Daleks were entombed in their original laboratory.
Centuries later, the Daleks had emerged, constructed an elaborate city and now appeared content to exist in peace on Skaro alone. However, they discovered that the Thals had also survived, now a race of peaceful pacifists, and attempted to destroy them. The Doctor, in what was by his own internal chronology his first encounter with the Daleks, prevented them from succeeding and helped shut down the city, destroying the Daleks present. However, it was later revealed that the Daleks had spread across the face of Skaro and founded other cities, and soon begun a new war with the Thals.
Events from this point forward are confusing and contradictory. The Daleks became a space-faring civilisation and, by their own internal chronology, had their first encounter with the humans of Earth in the mid-21st Century when they encountered an early human colony world, Vulcan. The intervention of the Doctor again ensured the defeat of the Daleks. The Daleks then invaded Earth itself in the mid-22nd Century and occupied the planet for several years. The Doctor assisted Earth in liberating itself and the planet was able to rebuild with help from its colonies. From this point forwards Earth was in a state of almost permanent war with the Daleks whenever they were encountered. Three centuries after this time the Daleks, allied with another Time Lord, the Master, almost succeeded in triggering a war between Earth and the Draconian Empire, but were exposed. The humans and Draconians launched a joint war against the Daleks which drove them from Earth's corner of the Galaxy (apparently including Skaro, which was abandoned). An attempted Dalek counter-attack using a vast army secreted on the jungle planet of Spiridon was defeated by a Thal guerrilla squad aided by the Doctor (who froze the 10,000-strong Dalek army), whilst a Dalek ship fleeing from the warzone was destroyed on the planet Exxilon.
Some time after this point the Daleks developed primitive time travel technology and sent an extermination squad in pursuit of the Doctor, hoping to kill him in his first incarnation and undo their previous defeats at the hands of his later incarnations. This plan failed and the Dalek squad was destroyed by a race of robots known as the Mechanoids.
Following their war with Earth and Draconus, the weakened Daleks came into another war, this time with a race of powerful androids known as the Movellans. The two races fought one another to a stalemate, with the two sides unable to break the impasse. A small team returned to Skaro and retrieved their creator Davros (now revealed to have been in suspended animation since the Daleks' creation, centuries or millennia later), banking on his knowledge of Dalek genetics and intelligence to create a solution to the impasse. Whilst they succeeded in rescuing Davros, the retrieval team was destroyed by a Movellan strike force and Davros was apprehended by humans and imprisoned in a penal facility.
Ninety years later, the Daleks stormed the facility and again rescued Davros, this time to find a cure for a Movellan virus that was wiping the species out. Davros, aware of the Daleks' capacity for betrayal, instead seized control of several Daleks in an attempt to create his own faction of Daleks completely loyal to him, although these were destroyed in battle with the 'real' Daleks. He escaped from the penal colony in an escape pod (having been adversely affected by the Movellan virus himself) and found his way to a human retirement colony, Tranquil Repose, where he used the genetic material of the residents to create a new race of Daleks. However, the 'main' Dalek faction led by the Dalek Supreme was alerted to Davros' plan and captured him, destroying Davros' Daleks in the process. Davros' fate after this point is unclear, but it appears that he escaped and succeeded in creating an army of 'Imperial Daleks' under his control. One strong theory is that he retrieved the 10,000-strong Dalek army on Spiridon left frozen by the Doctor and adapted these into a powerful army that the original Daleks, who had been severely weakened by centuries of warfare against the Thals, humans, Draconians and Movellans, could not withstand. The original Daleks became known as 'renegade Daleks' whilst Davros' faction became dominant and retook control of Skaro.
This marked the beginning of the Dalek Civil War, which raged for an indeterminate amount of time before it was ended by the Doctor tricking Davros into using the Hand of Omega, a powerful Time Lord piece of technology, to destroy Skaro and the Imperial Dalek faction once and for all (although Davros, once again, escaped thanks to a handy escape pod). The renegade Daleks survived, but went to ground for some considerable time to rebuild and recover.
Imperial Daleks suffer heavy losses in battle with renegade Daleks during the Hand of Omega gambit in Remembrance of the Daleks (Season 25, 1988).
The Daleks re-emerged over a thousand years later when they forged an alliance between several races in an attempt to destroy Earth and its allies using a powerful weapon known as the Time Destructor. As to be expected, the Doctor again thwarted this plan. Frustrated with the ability of 'inferior' species to constantly defeat them, the Daleks attempted to distill the 'human factor' of ingenuity and intuition and add it to their genetic make-up, but thanks to the inevitable intervention of the Doctor this plan failed and instead a number of 'humanised' Daleks were created. The two Dalek factions fought one another apparently to the point of mutual annihilation, but the humanised Daleks were eventually overcome and destroyed. After this the Daleks attempted to change their own history by ensuring their invasion of Earth in the 22nd Century was not defeated, a major violation of the laws of time (although the Doctor was able to help restore the original timeline).
After this point the Daleks appear to have vanished from the Galaxy for a long period of time, many thousands of years, becoming considerably more advanced and powerful in their long exile. Aware of repeated attempts to destroy them by the Time Lords, the Daleks launched the 'Great Time War' against Gallifrey which saw the destruction of many worlds and species with battles raging over all of time and space. The war turned against the Time Lords, who prepared a weapon of last resort that would destroy the Daleks but also possibly the entire universe. The Doctor prevented them from using the weapon and on the last day of the Time War was able to destroy both the Daleks and Time Lords, sealing the entire war out of the reach of time travel technology. Unfortunately, the Doctor was not entirely successful and several Daleks survived, one falling through time to Earth in 2012 where it was destroyed, another - the Emperor Dalek - proceeding to the 202nd Century where it rebuilt its forces. This force was also destroyed, apparently marking the final end of the Dalek race. Inevitably, this proved not to be the case as it was discovered that four other Daleks - the elite Cult of Skaro - had taken refuge in interdimenisonal space during the Time War to escape the destruction of the Time Lords and Daleks. The Cult fought the Doctor on two occasions and all but one member was destroyed. The surviving Dalek somehow breached the Time War to rescue Davros, who was able to use Kaled genetic material (cloned from his own cells) to recreate the Dalek race in a massive assault on Earth and several other worlds, but this was defeated yet again by the Doctor. A single ship escaped from this battle and took refuge near Earth during World War II. The three surviving Daleks lured the Doctor to their ship, where he triggered a failsafe device which resulted in the creation of five powerful new Daleks, the 'new paradigm'. These new Daleks, markedly superior to their predecessors, destroyed the old Daleks and disappeared, ready to undertake new plans to conquer the universe and leaving the Doctor with his old foes once again on the loose.
Behind the Scenes
When Doctor Who was launched in November 1963, the production team envisaged it as a show that would alternate between telling educational stories set in the past and more escapist SF adventure yarns, the logic being that the latter stories would keep the audience tuning in. Whilst this plan was eventually abandoned - savvy audiences felt that the historical stories were too boring and audience figures plummeted every time one appeared, recovering when the show returned to an SF setting - it did allow the production team to plan ahead and budget accordingly (the historical stories, which could use stock BBC sets and costumes, tended to be cheaper). With the very first Doctor Who serial, An Unearthly Child, being a story set in caveman times the production team knew the second would be a big SF story, and called in veteran TV writer Terry Nation to write it. Nation came up with the idea of an alien race which had survived a nuclear war (at the time a hot topic, due to the ongoing Cold War and the Cuban Missile Crisis of just a year earlier) but been forced to merge with machines in order to survive.
The production team responded well to the concept and the serial - then dubbed The Mutants, later The Dead Planet but more commonly now called The Daleks - was put into production. The all-important element of the Daleks' design was handled by Raymond Cusick (after the original slated designer, a certain Ridley Scott, dropped out) and a company named Shawcraft built the original props (four Daleks for £500, about £2,000 in today's money and a significant chunk of the show's budget at the time). The Daleks were destroyed at the end of the seven-part serial and a return appearance was not envisaged. Indeed, due to disappointing ratings for the opening Unearthly Child serial, it was assumed that Doctor Who itself would not last more than a few more episodes after this serial was concluded. Instead, the Daleks proved an immediate hit, with children impersonating them in playgrounds and the show's ratings more than doubling from the opening serial. The Daleks had saved Doctor Who, and public demand for their return rapidly rose. 'Dalekmania', a frenzy for Dalek-related merchandise, is a term usually given to the period from the Daleks' first appearance in 1963 to the bombing of the second Dalek movie, Daleks Invasion Earth 2150 AD, in 1966.
The Daleks returned frequently during the first four seasons of Doctor Who, namely in The Dalek Invasion of Earth and The Chase in Season 2, Mission to the Unknown and the massive 12-part epic The Daleks' Masterplan in Season 3 and then in Power of the Daleks and Evil of the Daleks in Season 4. As mentioned above, they also appeared in two (relatively) big-budget feature films. However, by Season 4 the public had shown signs of tiring of the Daleks' regular reappearances. The second Dalek movie was a failure and the writers were keen to introduce other villains and monsters. Terry Nation was also trying to launch the Daleks in their own spin-off TV series, so it was decided to destroy the Daleks for good at the end of 1967's Evil of the Daleks.
After the Daleks' disappearance, Doctor Who's popularity remained high as the show entered the 'classic monster years' of the Second Doctor (Patrick Troughton)'s reign, with monsters such as the Cybermen, Ice Warriors and Robot Yetis (seriously) becoming very popular in their own turn. It wasn't until 1972, after Jon Pertwee had taken over as the Third Doctor, that the production team decided to return the Daleks to the series. Building on the five-year absence of the Doctor's deadliest foes, excitement was high for their return, and Season 9's Day of the Daleks was a big hit, so much so that the BBC decided to return to using the Daleks on an annual basis. Season 10 saw them return with Frontier in Space (in which they teamed up with the Doctor's other deadliest foe, the Master) and Planet of the Daleks and in Season 11 in Death to the Daleks.
However, again creative fatigue on the part of the producers and ennui on the side of the viewers meant that excitement for more Dalek adventures was starting to ebb. The producers took the decision to again temporarily retire the Daleks in Season 12's story. Looking to do something different, Terry Nation took the step of writing a story in which the Doctor is given the opportunity to destroy the Daleks at the moment of their creation, but fails. The resulting story, Genesis of the Daleks, is frequently cited as one of Doctor Who's single most popular stories and is notable for introducing the character of Davros, the Daleks' creator.
The Daleks returned briefly in Season 17's Destiny of the Daleks and for a cameo in Season 20's The Five Doctors, but regular reappearances did not resume until Season 21's Resurrection of the Daleks. Producer John Nathan-Turner had appeared hesitant to rely on old or established enemies, but after achieving a major success with reintroducing the Cybermen after a long absence in Seasons 19 and 20, he decided to do the same with the Daleks. Writer Eric Saward was fascinated by the character of Davros and resurrected him as well, and Davros and his machinations were the focal points for both Resurrection and Season 22's Revelation of the Daleks. Some fans objected to the sidelining of the Daleks in favour of their creator, although Saward did establish an interesting recurring storyline with Davros attempting to create a new race of Daleks loyal to him in both serials. Doctor Who's near-cancellation in 1986 and Saward's departure saw this story abandoned for a while before the Daleks were brought back in Season 25's Remembrance of the Daleks as part of the show's quarter-century celebrations. Writer Ben Aaronovitch ran with some of Saward's ideas, with the Daleks now revealed to have been split into two factions battling one another for supremacy and returning to Terry Nation's ideas of the Daleks being obsessed with racial purity and eugenics.
Doctor Who was put on 'indefinite hiatus' after Season 26 in 1989, and the show remained off the air for sixteen years. During this time the Daleks continued to appear in spin-off comics and occasionally novels (of dubious canonicity). When Doctor Who was restored in 2005, it was inevitable that the Daleks would also return, and so it proved. New producer Russell T. Davies made the Daleks an integeral part of the restored series continuity, in which the Time Lords and Daleks had fought a 'Great Time War' leading to their mutual destruction. Inevitably, the Doctor would encounter survivors, leading to Dalek appearances in Season 27's Dalek, Parting of the Ways and Bad Wolf, Season 28's Army of Ghosts and Doomsday, Season 29's Daleks in Manhattan and Evolution of the Daleks, Season 30's The Stolen Earth and Journey's End, and Season 31's Victory of the Daleks. These frequent reappearances of the Daleks would again lead to some fans complaining of overuse of the Daleks and boredom with their predictable reappearances (appearing in three out of the four big season finales, for example).
With Davies' departure, incoming new producer Steven Moffat decided on a broad revamp of the series, with the introduction of a new Doctor (played by Matt Smith), a new companion, a new TARDIS set and exterior prop, a new title sequence and new music. He also decided to revamp the Daleks, giving them arguably the biggest changes in their design in forty-seven years. He also decided that the Doctor constantly encountering the 'last surviving' Daleks who then somehow escaped (or were destroyed, only for yet more 'last surviving' Daleks to show up elsewhere) was getting repetitive, so had the Daleks restored as a race and force to be reckoned with in Victory of the Daleks.
The Daleks' return in Doctor Who is inevitable, though hopefully not in the too-near future (though the sheer cost of building the new Dalek casings means that the production team might decide to return to them in the currently-airing 31st season). The Daleks are an intriguing race, created when World War II and Nazism was still fresh in the mind, and a formidable foe for the Doctor whenever they appear. However, as the above shows, their threat level tends to diminish whenever they appear too frequently, and their seeming inability to kill the Doctor or even win once in a while reduces their credibility as villains. It is notable that, arguably, the single most effective use of the Daleks is in the 2005 episode Dalek, when one single Dalek wipes out dozens of people trying to destroy it and is defeated only by a fluke (contrived as that is) rather than the Doctor's ingenuity. That episode felt more tense and threatening than when hundreds of them were flying around in any of the big season finales. It will be interesting to see what Moffat and the rest of the new Doctor Who production team will come up for their next appearance.
The Daleks (1963-64)
The Dalek Invasion of Earth (1964)
The Chase (1965)
Mission to the Unknown (1965)
The Daleks' Masterplan (1965-66)
Power of the Daleks (1966)
Evil of the Daleks (1967)
Day of the Daleks (1972)
Frontier in Space (1973)
Planet of the Daleks (1973)
Death to the Daleks (1974)
Genesis of the Daleks (1975)
Destiny of the Daleks (1979)
Resurrection of the Daleks (1984)
Revelation of the Daleks (1985)
Remembrance of the Daleks (1988)
Bad Wolf (2005)
The Parting of the Ways (2005)
Army of Ghosts (2006)
Daleks in Manhattan (2007)
Evolution of the Daleks (2007)
The Stolen Earth (2008)
Journey's End (2008)
Victory of the Daleks (2010)