DALEKS 

Created by Davros, the Daleks were the mutated descendants of the Kaleds (a.k.a. Dals), one of the two races living on the planet Skaro. The Daleks lived inside a mobile casing which was equipped with sensor discs, a unique iris and lens, a sucker-stick arm and a special extermination weapon. Their natural form appeared to be small, green, blob-like, octopods with claws. They had one purpose: to exterminate all other life-forms and become the dominant species in the universe. The Emperor Dalek was the supreme Dalek leader. Mention was made of a Dalek Council, presumably reporting to the Emperor. Beneath it were warlords such as the Black or Gold Daleks.
The Daleks' history is subject to different interpretations. It is said that the Daleks began as a humanoid race first known as Dals, then later as Kaleds, on planet Skaro. Their enemies were the Thals, with whom they engaged in fierce warfare, lasting a thousand years, culminating with the neutronic wars which destroyed most of Skaro and made it radioactive. The Kaled scientist Davros studied and further developed some of the mutations resulting from the wars, then created a mobile casing for them and christened his new creatures Daleks. The Daleks' mobile casing was based on Davros's own life support chair. Earlier versions were powered by static electricity. Later versions used various forms of energy, including solar power.
The Time Lords sent the Fourth Doctor to Skaro to stop the development of the Daleks, but he failed, succeeding only in entombing them in the Kaled bunker, after they had turned against their creator (4E).
Later, some crippled Kaled survivors discovered the remnants of Davros' early experiments and mutated themselves into new Daleks. The First Doctor met the new Daleks in the Dalek City and foiled their attempt to destroy the surviving Thals by increasing Skaro's radiation levels. Those new Daleks presumably perished when the Thals destroyed their power controls (B).
The original Daleks ultimately resurfaced and took over Skaro, driving the Thals in exile. Their ruthlessness enabled them to conquer their space sector. Mankind's slow but steady space expansion attracted the Daleks' attention. By 2160 AD, the Daleks launched a secret plan to invade Earth. First, they spread virulent plagues through a swarm of meteorites. As a result, the solar system was quarantined by the other human colonies. The Daleks struck in 2164 AD, invading an almost depopulated Earth. Any attempt at space intervention was firmly dealt with by the Daleks' space fleet. This became known as the First Dalek War. The Daleks planned to extract Earth's molten core and turn the planet into a giant spaceship. But, in 2167 AD, the First Doctor, Susan, Ian Chesterton and Barbara Wright helped freedom fighters Dortmun, Tyler and David Campbell defeat the invaders (K).
(The same invasion succeeded on a parallel Earth where World War Three had occurred, but was eventually erased from the time continuum when the Third Doctor prevented the death of 20th Century diplomat, Sir Reginald Styles (KKK).)
Some Daleks who had survived this First Dalek War crashed on Vulcan and later tried to take over the human colony there, but were defeated by the Second Doctor, Ben Jackson and Polly (EE).
Earth fought the Daleks again after they tried to blackmail the galaxy by controlling the only supply of parrinium (a mineral found only on Exxilon), the cure to a space plague, which the Daleks had probably started. They were thwarted by the Third Doctor, Sarah Jane Smith and Earth's Marine Space Corps (XXX). Once the Daleks' role in the space plague became known, several galactic races (including the Draconians), probably stirred up by the exiled Thals, united to attack and punish the Daleks. Thus was born the Alliance. The war that ensued became known as the Second Dalek War. The Daleks were then driven from Skaro, which was retaken by the Thals. The Daleks were forced to relocate to another world which, out of pride, they christened Skaro (herein dubbed "Skaro II").
Circa 2540 AD, the Daleks decided that their best tactic would be to create a split between the Alliance's two most powerful members: Earth and Draconia. They engaged the services of the Master to foment a war between the humans and the Draconians, even offering him the use of their Ogron slaves. But the Master's scheme was exposed and defeated by the efforts of the Third Doctor and Jo Grant (QQQ).
The Daleks then plotted to attack the Alliance with the secret of invisibility and a 10,000-strong Dalek army, kept frozen on Spiridon. The Third Doctor and Jo, with the help of a Thal commando unit that had been monitoring the Daleks' moves from Skaro, thwarted them again (SSS). The Thals notified the Alliance of the Daleks' activities, and the Alliance struck back, leading to the Third Dalek War. At one point during this war, a Dalek casing was put on exhibit in the Moroks' Space Museum, and provided a hiding place for the First Doctor (Q). Also, a Dalek was used by Borusa as a pawn in the Game of Rassilon (6K).
The Daleks eventually took advantage of the Alliance's slow disintegration during the 26th Century to launch an attack on Skaro. They succeeded in exterminating most of the Thals, but the planet itself was turned into a bombed-out ruin of no further use to them -- or so they thought. Towards the end of the 26th Century, the Daleks encountered the equally aggressive robotic Movellans, which they could not crush. Caught between the still powerful Alliance and the undefeated Movellans, the Daleks felt trapped. So, as the 27th Century began, they returned to Skaro to recover their long-buried creator, Davros. But their efforts were thwarted by the Fourth Doctor and Romana. Davros was taken to Earth where he was sentenced to life in suspended animation (5J).
Deprived of Davros' help, the Daleks lost their war against the Movellans, who used a special virus to decimate them. While striving to defeat the Movellans, the Daleks had become aware of the Time Lords' existence and discovered the rudiments of time travel technology, involving the use of time corridors. Ninety years after Davros' trial, the Daleks hired Lytton to free Davros from the space penitentiary where he was kept. They also captured the Fifth Doctor and plotted to use him against the Time Lords, who had presumably tried to stop the Daleks' discovery of time travel. The Doctor defeated the Daleks but Davros escaped, now intent on creating new Daleks, subservient only to him (6P).
Davros secretly relocated to Nekros where, posing as the Great Healer, he used the bodies stored in the mortuary known as Tranquil Repose to create his own White (or Imperial) Daleks. But he was exposed and defeated by the Sixth Doctor. Davros was taken back to Skaro II by the Daleks (6Z).
Davros presumably escaped, since he and the Daleks fought again in or about 2963 AD. The two camps used their time corridor technology to travel back in time to 1963 London to capture the Hand of Omega. As a result of the Seventh Doctor's intervention, both Dalek races were utterly devastated. Either Skaro's, or Skaro II's, sun was destroyed. However, Davros, who had already taken to calling himself the Emperor Dalek, escaped (7H).
A long period of inactivity ensued. Sometime between the 32nd and 38th Centuries, the Daleks restored Skaro (or Skaro II?) to its former glory. They also refined their time travel technology. Using taranium, they were now able to build crude time machines. One of their first enterprises was to send an exterminating team to chase the First Doctor, Vicki, Ian and Barbara through time and space. The Dalek squad was eventually destroyed by the Mechanoids (Q).
Circa 4000 AD, the Daleks again tried to take over the Solar System which they perceived (possibly blinded by their centuries-old feud with mankind) as the Federation's lynchpin. This time, they allied themselves with other space races (including Galaxy 5). This became known as the Fourth Dalek War.
The Dalek invasion plans were first discovered on planet Kembel by Space Security Agent Marc Cory, who was murdered by the Daleks (T/A).
Soon afterwards, the First Doctor, Steven Taylor and Katarina arrived on Kembel, and discovered a tape left by Cory. With the help of another space Security Agent, Bret Vyon, they decided to warn Earth of the impending Dalek attack, and of the treachery of Mavic Chen, the Guardian of the Solar System. Chen had given the Dalek the replacement taranium they needed to activate their supreme weapon: the Time Destructor.
The time travellers stole the Daleks' taranium core, and fled Kembel. In the course of their escape, Katarina sacrificed herself to save her companions. Bret Vyon was killed by his sister, Sara Kingdom, who later found out the truth and helped the Doctor. When the Time Destructor was finally activated, it was on Kembel, which put a stop to the Dalek invasion. Unfortunately, its deadly effects also killed Sara Kingdom (V).
Presumably, the Federation then retaliated, and the Daleks were again driven back to Skaro, their power and influence severely curtailed.
A Century or so later, however, the Daleks managed to obtain some more taranium, and decided again to use their time travel capabilities to attack Earth. By then, they were ruled by an Emperor Dalek, who could very well have been Davros, after possibly subjecting himself to further mutations.
Resorting again to their favourite weapon, the biological one, the Daleks planned to infect humanity with the Dalek factor. Having detected Prof. Waterfield's early time travel experiments, the Daleks travelled to 1866 AD Earth. The Emperor's efforts were thwarted by the Second Doctor, Jamie and Victoria Waterfield. Instead of infecting Mankind, it was the Daleks themselves who became contaminated with the Human Factor. A "civil war " in which the Dalek race perished erupted on Skaro (LL).
However, some humanized Daleks may have survived, thereby making the Fourth Doctor's prophecy that eventually a greater good would come of the Daleks' creation come true (4E). The fact that the Daleks eventually become extinct, thanks mostly to the intervention of the Doctor (often manipulated by the Celestial Intervention Agency), may be evidence of Time Lord intervention.