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.)

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.