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)

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
By one account, during the neutronic war, the humanoid Dalek Warlord Zolfian tasked his Chief Scientist Yarvelling with creating an army of Dalek War Machines for use against the Thals. Originally robotic, these War Machines came to be used as casings by the surviving Dalek mutants. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, COMIC: Genesis of Evil)

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)

In the Vulcan Incident, a group of three Daleks who had crashed in their space capsule years prior went about creating new Daleks whilst acting as servants to the human colonists who had reactivated them. Their intention was to form an army of Daleks which would take over the planet Vulcan and exterminate the humans. However, these Daleks were destroyed by the Second Doctor. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, TV: The Power of the Daleks)

By implanting the Human Factor on a number of Daleks, the Second Doctor created an army of humanised Daleks which turned against the Emperor and his Black Dalek Leaders, instigating the Dalek Civil War. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, TV: The Evil of the Daleks)

During the Duplicate Incident, Davros, in an attempt to dissuade the Fifth Doctor from killing him, offered him "total power at the head of a new Dalek army". Having previously been betrayed by the Daleks, Davros sought to secure control of his own Dalek army, first by using a indoctrination serum hypodermic to condition a number of Daleks and Dalek duplicates to serve him, challenging the authority of the Supreme Dalek. However, these new servants were killed in battle. (TV: Resurrection of the Daleks)

Davros eventually escaped to Necros, where he set himself up as the Great Healer of Tranquil Repose. There, he used the bodies of the human Resting Ones to create a new army of Daleks loyal to him, (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) amounting to several thousand. (PROSE: Revelation of the Daleks) The Skaro-faction Daleks were alerted to the existence of these new Necros Daleks by Lancelot Takis, and sent a ship to Necros. Fighting their way through Davros's Daleks, the Daleks apprehended Davros and proceeded to take him back to Skaro to stand trial. As for the Daleks he had created, they were to be reconditioned to obey the Supreme Dalek. However, Orcini set off an explosion in Davros' bunker, killing many of his prototype Daleks. (TV: Revelation of the Daleks)

The Dalek Survival Guide claimed that the Necros Daleks were all destroyed by the Skaro-faction Daleks when they captured Davros, (PROSE: Dalek Survival Guide) whilst the Time Lords suspected that some of the Necros Dalek survivors could have been present on Skaro during Davros's trial, speculating that they were the Daleks who helped Davros cement his control and establish the Imperium. They did, however, recognise that the destruction of Davros's work on Necros deprived the Daleks of an opportunity to reproduce from any genetic stock, an ability which they would not master until the Last Great Time War. (PROSE: Dalek Combat Training Manual)

Davros later created a refined "Imperial Dalek army", (PROSE: Dalek Combat Training Manual) who followed himself as Emperor Dalek. The Imperial Daleks fought in a civil war against the Renegade Daleks under the Supreme Dalek, only for both sides to be defeated by the Seventh Doctor in the Hand of Omega Incident. (TV: Remembrance of the Daleks)

In the Dalek Combat Training Manual, published during the Time War, the Time Lords acknowledged that the Dalek army they currently faced seemed to be once more united following the civil war. (PROSE: Dalek Combat Training Manual)

Having survived the Time War, the wartime 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)

Composed of four Daleks, the Cult of Skaro escaped the Time War in the Void Ship known as the Sphere and brought with them the Genesis Ark, a dimensionally transcendental Time Lord prison ship containing millions of bronze Daleks, constituting an army. After the Cult of Skaro emerged on Earth in the 2000s, the Genesis Ark was opened, with the Dalek army attacking humans and the invading Cybus Cybermen alike in the Battle of Canary Wharf. The conflict was soon ended when the Tenth Doctor sent both the Daleks and the Cybermen into the Void. Though the Cult themselves used an emergency temporal shift escape, (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, TV: Doomsday) the Dalek forces remained in the Void and ultimately perished along with everything else trapped there as a result of a "greater battle". (TV: The Next Doctor)

Having escaped to Manhattan in 1930, the Cult of Skaro began the Final Experiment to continue the Dalek race. To that end, they acquired hundreds of human bodies and implanted them with Dalek DNA, creating an army of Dalek-humans. Dalek Sec himself transformed into a Human-Dalek after merging with Diagoras and was to assume the position of Controller but was overthrown by the rest of the Cult when he attempted to work with the Doctor to make the army more human. Assuming the position of Controller, Dalek Caan used a military computer to direct the Dalek-humans in an invasion of Manhattan, only for them to refuse to obey the Daleks as the Doctor's interference resulted in his Time Lord DNA being mixed in with them. When subjected to an attack, the Dalek-humans fought back and destroyed both Daleks Jast and Thay but were all terminated by Caan in an act which the Doctor denounced as genocide. Recognising that Caan was now the last Dalek in existence, the Doctor offered his help only for Caan to escape using another temporal shift. (TV: Evolution of the Daleks)

Going back to the first year of the Time War, Caan rescued Davros from death and returned to the post-Time War universe, with Davros using his own DNA to create a new army of Daleks, forming a New Dalek Empire led by a Supreme Dalek, based at the Crucible and fielding a new Dalek Fleet. In the Planetary Relocation Incident, the New Dalek Empire assembled a number of stolen planets including Earth in the Medusa Cascade, where they served as an engine for the reality bomb which Davros intended to use to destroy all other life across the multiverse. However, Caan himself thwarted the Daleks by ensuring that Donna Noble would be present to become the DoctorDonna and stop the reality bomb. The DoctorDonna was created as part of a metacrisis alongside the Meta-Crisis Tenth Doctor who, at Caan's urging, used the Dalekanium power feeds to destroy the Crucible along with the New Dalek Empire. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, TV: The Stolen Earth/Journey's End)

However, one ship from the New Dalek Empire survived and, using a Progenitor device, created a New Dalek Paradigm. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, TV: Victory of the Daleks) After returning to their own time in the far future, (TV: Victory of the Daleks, PROSE: Dalek Combat Training Manual) the New Paradigm designated the first of the new Drone Daleks, distinguished by its red casing, to command the Dalek armies which were created when they utilised the weapon-generators of Goth to produce millions of Drone Daleks in its image.

In light of the repeated failures of the New Dalek Paradigm, the Daleks reformed their empire into the Resurrected Dalek Empire. The Prime Minister of the Daleks had the Red Drones of the Dalek Imperial Army]] replaced by the bronze Daleks associated with the Time War so as to provoke the most fear across the universe. The larger Red Drones became an officer class, albeit one kept safely away from the front line. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

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)

Behind the scenes

 * The Visual Dictionary stated that the Dalek army in the Battle of Canary Wharf was composed of legions, observing that the bronze "Battle Daleks" flew in squadrons of 12 or 16.