Dalek Earthforce

The Dalek Earthforce were the contingent of Daleks which were assigned to Earth during the 22nd century Dalek invasion. (PROSE: Doctor Who and the Dalek Invasion of Earth)

Hierarchy
The Dalek Earthforce was mostly made up of basic silver Daleks. A Black Supreme Controller was designated Commander of the Dalek Earthforce. In addition, a Dalek saucer commander, a black and silver Dalek, served aboard the Dalek flying saucer. (TV: The Dalek Invasion of Earth, PROSE: Doctor Who and the Dalek Invasion of Earth)

Characteristics
The Daleks of the Dalek Earthforce resembled the silver Dalek War Machines which were encountered on Skaro by the First Doctor. (TV: The Daleks) However, they were distinguished by a discs which was attached to were the back of the casing's middle section. Discussing the change in appearance, the Doctor and Ian Chesterton recalled that the Daleks they had met could only move on metal within the Dalek City, to which Ian suggested that the discs may have accounted for their increased mobility on Earth. Indeed, during the occupation, the Daleks were able to traverse various forms of terrain. (TV: The Dalek Invasion of Earth) Later Daleks lacked the discs while retaining their increased mobility, instead sporting a series of slats across the middle section. (TV: The Chase et al.)

History
The first incident of the invasion came in 2157, (PROSE: Lucifer Rising) when Earth was bombarded with meteorites. At first this was thought the result of a cosmic storm, but shortly after things had returned to normal, people started dying of a new plague sent by the Daleks via the meteorites. The majority of the population of Africa, Asia and South America died before humans could find a cure. (TV: The Dalek Invasion of Earth)

The Daleks held the Earth for about ten years. During the occupation period, small groups of human resistance fighters continued to exist. (TV: The Dalek Invasion of Earth)

The Sixth Doctor and Peri Brown landed in 2163. The Daleks were unfamiliar with the Doctor, thinking he was a human. The Doctor was interrogated by a Black Dalek. He foiled the Daleks' plan to unleash a Varga plant virus. The Doctor and Peri also defeated the Roboman Elite and erased any record of his involvement afterwards but the invasion continued to ensure the First Doctor finally put an end to it. (AUDIO: Masters of Earth)

The Daleks commenced a mining operation in Bedfordshire in order to reach the Earth's magnetic core, replace it with a propulsion system, and turn the whole planet into a massive spacecraft to conquer the galaxy. (TV: The Dalek Invasion of Earth)

In 2167, (AUDIO: The Mutant Phase) the Daleks announced that they would destroy London. A freedom fighter named Dortmun, who had been developing explosives, initiated an attack on the Daleks' saucer at the London helipad. Although the attack liberated several prisoners of the Daleks, the bombs did not work effectively against the Daleks, leading to several casualties. Ian Chesterton, who had accompanied the freedom fighters, remained on the saucer as it travelled to Bedfordshire.

Following the saucer attack, the Dalek Supreme Command issued an order for the destruction of what remained of London using firebombs. One of these firebombs was placed near one of the resistance base entrances, which the First Doctor, Susan and David Campbell were hiding beside. David spotted the bomb soon after, and was able to disable it by using acid from Dortmum's bombs to burn through the casing and remove the internal mechanism of the firebomb.

Some of the resistance fighters, including the Doctor, Susan and David, from London to the site of the Daleks' mining operation at Bedfordshire. Barbara Wright and Jenny also (independently) made their way towards Bedfordshire, but were captured. They all, however, assisted in the final destruction of the centre of Dalek operations on Earth. (TV: The Dalek Invasion of Earth)

Behind the scenes
In the theatrical adaptation Daleks' Invasion Earth 2150 A.D., the Supreme Controller's role was replaced by two Daleks, a Gold Dalek and their subordinate Black Dalek, while a Red Dalek functioned as saucer commander, while the basic Daleks were likewise coloured silver. Unlike The Dalek Invasion of Earth, the Daleks lacked discs, instead sporting the slats which had been introduced in The Chase.