Dalek army
The "Dalek army" referred to the gathered forces of the Dalek race, (TV: Resurrection of the Daleks) typically when discussing their ground forces. (TV: Planet of the Daleks, et. al) However, the ability for Daleks to operate in atmospheres (TV: The Stolen Earth) and space through flight meant a "Dalek army" could do more than simply attack on ground. (TV: The Parting of the Ways) The Dalek army could thus besiege and attack locations in space, in atmospheres, and on ground, (TV: The Parting of the Ways, The Stolen Earth) attacking targets by flying above or landing on the ground. (TV: Doomsday)
During a Dalek invasion, the Dalek army would work alongside the Dalek Fleet, with Daleks operating in the fleet easily joining the "army" unit if the attack called for it. (TV: The Parting of the Ways, Revolution of the Daleks) Being a warrior race totally focused on conquest and extermination, (TV: The Witch's Familiar, et. al) every individual Dalek was part of the overall Dalek army, even if that specific Dalek was currently operating aboard a warship of the Dalek Fleet branch. (TV: Resurrection of the Daleks, et. al) Despite therefore being part of the army and holding a command position within it, various Dalek officers, such as Supreme Daleks, would not see active combat and instead commanded away from the frontline. (AUDIO: Out of Time)
Structure
Formation
The overall army branch was divided into individual armies of Daleks, (TV: Planet of the Daleks, et. al) which could be further split into units as small as squads or large units, including battalions, (PROSE: Birth of a Legend) legions, (PROSE: The Third Wise Man) and divisions also existed under the overall (PROSE: Dalek Survival Guide)
As observed by Landinalakallinian, battalions were commanded by Dalek Captains, each battalion being comprised of two equal-sized companies commanded by a Dalek Lieutenant. Dalek Captains and Lieutenants did not seem to be distinguishable from exterior appearance, with the Gallifreyan professor suggesting that they relied on forms of radio identification signals to identify each other instead of more obvious rank markings. (PROSE: The Dalek Problem)
Tactics
For Dalek invasions, Dalek saucers or other such ships would attack from above, while Dalek ground forces would attack on the ground or while flying themselves. (TV: The Last Day, The Day of the Doctor, et. al)
History
The Dalek Empire named its overall army branch the Imperial Dalek Army. (COMIC: Emperor of the Daleks!) The New Dalek Paradigm and Resurrected Dalek Empire called their overall army the Dalek Imperial Army. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)
Having survived the Last Great Time War, the Dalek Emperor created what the Ninth Doctor identified as an "army of Daleks out of the dead", having harvested humans to create new Daleks. Aboard the Game Station, Captain Jack Harkness likewise identified the Daleks as an invading army. This army, along with the Dalek Fleet and the Emperor himself, were all destroyed by Rose Tyler as the Bad Wolf. (TV: The Parting of the Ways)
Upon taking control of Defence Drone casings, Dalek mutants created from human DNA heralded themselves as the "New Dalek Army", only to be exterminated by a Dalek Death Squad which the Thirteenth Doctor had lured to Earth. (TV: Revolution of the Daleks)
