Thousand Year War

The Thousand Year War pitted the two indigenous peoples of Skaro, the Kaleds and the Thals, against one another. The conflict ravaged the planet with radiation, forcing the remaining combatants to live within domed cities. The war created a third race of sorts in the Mutos, made outcasts due to their disfigurement. Even as the cause of the war was lost to memory, both sides remained committed to victory - and the Kaleds achieved a scientific breakthrough when Davros engineered the Daleks.

Causes
By the latter stages of the war, neither the Kaleds nor the Thals could remember why it had started. (AUDIO: Davros)

By the time that the Fourth Doctor visited Skaro on a mission to prevent the creation of the Daleks, the Thals and Kaleds lived in two domed cities overlooking a polluted wasteland. The Scientific Elite, headed by Davros and his assistant Nyder, and a Military Elite hoped to create weapons that would finally bring victory. The use of nuclear, chemical and biological weapons had led to genetic mutations among both Thals and Kaleds, disparagingly referred to as Mutos. The Mutos were driven out by the Thals and the Kaleds to keep their races pure.

By this time both sides had become so desperate for soldiers that they were deploying boys in their early teens on the battlefield and the chief Kaled commander, General Ravon, was a young man in his early twenties. (TV: Genesis of the Daleks)

Weapons and technology
An anachronistic mixture of technologies on the battlefield showed a society which had devolved rather than evolved, with combatants using energy weapons alongside rifles and machine guns and engaging in trench warfare as in Earth's early 20th century. Their uniforms were frequently mismatched - soldiers could be seen wearing modern combat jackets made of synthetic fibre with other articles of uniform made of leather.

When the Time Lords sent him and his companions Sarah Jane and Harry to Skaro to avert the creation of the Daleks, the Fourth Doctor speculated the Kaleds and the Thals had been fighting for so long that when the war had begun they had both started out with the most modern equipment, but as the centuries passed they lost the resources and had to make do with what they had. Indeed, General Ravon, one of the commanders of the Kaled army, harshly reminded one of his underlings ammunition was valuable and could not be wasted.

In the long-range, as well as the biological and nuclear weapons already mentioned, both sides used chemical rockets. Towards the end of the war, the Thals intended to use a neutronic missile against the Kaleds. (TV: Genesis of the Daleks)

On the battlefield, mutant Handmines were used. Kanzo was pulled underground by one, while a boy Davros, having been lost on the battlefield of the War, was surrounded by them. At that point, both laser-firing biplanes and bows were used on the battlefield. (TV: The Magician's Apprentice) After an encounter with a future version of Davros, the Twelfth Doctor rescued Davros from the battlefield in order to teach him the concept of mercy. (TV: The Witch's Familiar)

Conclusion
Davros gave the Thals information to allow them to breach the Kaled Dome, causing massive casualties amongst Davros' own people.

This provided a rationale for the Kaleds in turn to set the newly created Daleks against the Thals. At last, a Thal rocket destroyed the Kaled Dome. Thals, led by Bettan and Mutos, led by Sevrin, joined to fight against the Daleks emerging from the ruined Kaled city. (TV: Genesis of the Daleks)

The records held by the Daleks and the Thals from over five hundred years after the war ended were heavily corrupted, describing the war as just a quick neutronic war, and not lasting for centuries. According to Alydon, Skaro, which Alydon described as "a great world, full of ideas and art and invention", was destroyed in one day. (TV: "The Expedition") One Dalek claimed that after the neutronic war, the Daleks' "forefathers" retired into the Dalek City, and protected themselves from the fallout inside their machines. (TV: "The Survivors")

Alternate timeline
In an alternate timeline, the war, known as the Neutron War, was caused accidentally. Though the Daleks still developed, in this timeline they became peace-loving academics. Skaro was the universal centre of civilisation, philosophy, democracy and art, visited from all over the universe. (PROSE: The Ripple Effect)

Behind the scenes

 * According to the non-narrative reference book Doctor Who: The Dalek Handbook, the war lasted from 450 AD to 1450 AD.

Rhyfel Mil Flwyddyn Tausendjähriger Krieg Guerra de los Mil Años