On relisten, the Dalek Supreme actually announces the Harvesting of Urbinia. It's still the most accurate name for the invasion there is.
Talk about it here.
In an alternate timeline, the Harvesting of Urbinia was declared by the Dalek Supreme when the Daleks invaded the planet Urbinia. Armed with the operational Time Destructor, the Daleks were intent on enslaving the population. (AUDIO: Daughter of the Gods)
History
Origin
The nightmare begins
The Time Destructor's taranium core, which was originally stolen by the First Doctor after his arrival on Kembel. (TV: The Daleks' Master Plan)
In the 40th century, the Dalek Empire began preying on human space. Planning an ambitious assault on Mutter's Spiral and the solar system in particular, they assembled a warforce collectively represented by delegates from the Outer Galaxies (TV: Mission to the Unknown) The Daleks' coup de grace was to be the Time Destructor, a taranium-powered superweapon capable of manipulating time by accelerating it backwards or forwards at a rapid pace. By 4000 AD, development of the device was almost complete. (TV: The Daleks' Master Plan)
The disruption of time
The Doctor, Steven Taylor and Katarina living on Urbinia, oblivious to the timeline disturbance. (AUDIO: Daughter of the Gods)
The First Doctor was meant to interfere with the Daleks' invasion preparations and foil the attempt to use the Time Destructor. However, after departing the city of Troy at the end of the Trojan War, the Doctor's TARDIS collided with its future self, piloted by the Second Doctor, while in flight through the Time Vortex. The First Doctor never reached his original destination, the hidden Dalek outpost on Kembel, and instead landed on Urbinia. This created a new timeline in which the Daleks' development of the Time Destructor proceeded apace, whilst the Doctor remained unaware of the impending galactic invasion.
Unable to easily repair the TARDIS, the Doctor and his companions, Steven Taylor and Katarina, spent three months in the Urbinian capital city of Kiria. During that time, the Doctor mingled with the scientific community and delivered various lectures on scientific principals such as alchemy, earning a strong reputation among the elite and even sparking a friendship with Chancellor Atrias.
Destruction of Baralda and the Dalek ultimatum
At the end of those three months, the Dalek Fleet arrived in the Third Galaxy and struck at Urbinia's neighbouring planet Baralda. The Baraldans were quickly overwhelmed. First Citizen Togrok attempted to contact Urbinia for aid, but as the message was recorded, the Time Destructor was activated and the planet, together with all life on it, rapidly aged to the point of disintegration.
The destruction of Baralda was used as a show of force by the Daleks, intended to force Urbinia's swift surrender. The attack happened so fast that the Council in Kiria City was unable to meet to discuss the crisis. Chancellor Atrias was only able to summon the Doctor and seek his advice. The Dalek Supreme opened contact with Atrias and laid out the Dalek terms: their intention was to subjugate the Urbinian population as slave labour; failing this, the planet would be destroyed.
Atrias offered to surrender to the Daleks immediately and attempted to flee the planet before the fleet arrived. The Doctor and Captain Parlos of the Urbinian security forces were appalled by his display of cowardice and poor leadership and stood up to take on the burden themselves. The Doctor recommended a worldwide evacuation. Meanwhile, as the Dalek Fleet approached, the Dalek Supreme declared the beginning of the Harvesting of Urbinia.
The Harvesting of Urbinia
Evacuation and preliminary bombardment
Despite Atrias agreeing to surrender, the Doctor and Parlos did not enforce it. All Urbinian cities began localised evacuations. Civilians in Kiria were ordered to travel to the city's one spaceport where Steven Taylor was working. Detecting mass population movement, the Daleks began to bombard the cities as a further warning for the Urbinians to stand down. Looting took place in the abandoned streets.
The Second Doctor, Jamie McCrimmon and Zoe Heriot arrived in Kiria in the midst of the evacuation, having just landed after the TARDIS collision from their own perspective. Having no memory of the event, the Doctor realised his original incarnation was not meant to have come to Urbinia. He volunteered to aid in the evacuation effort in order to meet with his younger self in the Council Chamber, while Zoe helped Steven prepare the ships. Zoe calculated the coordinates necessary for the ships to avoid the Dalek Fleet while leaving the planet and advised that all ships leave at the same time so the Daleks would not realise what was happening in time.
The evacuation went poorly. With so little time to organise anything, starships and spacecrafts of all types and ages were put to use. Food supplies were woefully inadequate to last more than a few days in flight, and the crowds continually panicked despite the efforts of Parlos and the security officers to maintain a semblance of order. Some guards even dropped their responsibilities in panic themselves. Ultimately, almost half the population of Kiria never made it to the spaceport and took their chances outside the city instead, or stayed indoors seeking shelter. Premature take-offs in other cities alerted the Daleks to the evacuation efforts, rendering Zoe's coordinates useless. Every ship that attempted to leave the planet was destroyed. All other cities surrendered and the Daleks turned their full attention to the ongoing resistance in Kiria.
Planetfall
Still awaiting a meaningful surrender, the Daleks landed a saucer to assert control on the ground. Parlos attacked the first Silver Daleks to emerge but the First Doctor called her off, lest the Daleks activate the Time Destructor in the face of serious hostilities. Instead, he instructed her to lure the Daleks away from the spaceport. Atrias was captured after his ship was stolen in the chaos and brought before the Dalek Supreme. He was exterminated after claiming he was no longer in charge.
The Second Doctor met with the First Doctor and explained the timeline discrepancy. Daleks stormed the Council Chamber and attempted to bring them before the Dalek Supreme but Parlos and her officers provided a distraction which allowed the Doctors to escape to the spaceport.
In the streets, the Daleks began to round up any Urbinians they could, and murdered many more. Three Daleks reached the spaceport ahead of the others and used Jamie and Katarina as hostages to gain entry to the hangar bay. They were destroyed in an ambush when Zoe detonated a volatile phason pod, igniting fuel deliberately spilled across the floor and engulfing the Daleks in intense flame. (AUDIO: Daughter of the Gods)
Deadline for surrender
In line with an old Dalek law, decreed by the Dalek Emperor after the first ever Dalek campaign, (COMIC: The Amaryll Challenge) and which later became a Dalek mantra, (TV: The Power of the Daleks) the Dalek Supreme decided that the Urbinians could not be conquered, so they would be destroyed.
Having run out of patience, the Dalek Supreme issued the Doctor with one last chance to surrender before the fleet deployed the Time Destructor. Even the Dalek ground forces were considered to have failed, and the Dalek Supreme viewed their potential annihilation by the Time Destructor as a just punishment. Even so, the Daleks on the ground continued to fight on as normal, advancing on the spaceport after successfully surrounding the area.
The Second Doctor was able to construct a replacement TARDIS circuit to repair his damaged console and allowed Katarina to decide whether he should use it, as he knew she did not survive the original course of events. Katarina offered her support and the Doctor promised the others that his success would stop the invasion from ever happening. He asked Parlos to distract the Daleks while he, Katarina, Jamie and Zoe made for his TARDIS. The First Doctor and Steven stayed behind to protect the civilians in the hangar bay.
Parlos engaged the Daleks once more and she died in the fighting. The Daleks made their way into the hangar bay and apprehended the First Doctor. Though they declared victory, the Doctor simply warned them that the struggle was "far from being all over!"
The Time Destructor was finally activated and Urbinia began to accelerate forward in time. The Second Doctor's companions quickly began to show the effects and fought hard to keep moving on. They reached the TARDIS and the Doctor pulled them all inside. Shielded from the effects, they reverted back to normal, but outside, Urbinia met the same fate as Baralda.
Timeline reset
After escaping the destruction of Urbinia, the Second Doctor replaced his broken TARDIS circuit and used the fast return switch to travel back to the point of the TARDIS's initial collision with itself. The three months spend on Urbinia were erased and the First Doctor's TARDIS avoided the Vortex crash after departing Troy. It landed on Kembel at the end of its intended flight. (AUDIO: Daughter of the Gods)
The Dalek Civil War, the true end to the Daleks' gambit. (TV: The Evil of the Daleks)
From there, the Doctor discovered the Dalek plans and stole the Time Destructor's taranium core. He ultimately gained control of the Time Destructor and turned it against the Daleks, although it came at a heavy cost – Katarina, as well as two other allies, Bret Vyon and Sara Kingdom, all died. The Dalek invasion force was wiped out and Kembel was ravaged before the core burnt itself out. (TV: The Daleks' Master Plan)
The sudden destruction of the invasion force was a massive blow for the Daleks but worse was to come once Earth discovered the plot. (PROSE: The Mutation of Time) The Great War began, lasting almost a thousand years (PROSE: The Evil of the Daleks) and ending with the near-total destruction of the Daleks. (TV: The Evil of the Daleks)
While the events of the Harvesting of Urbinia were undone, the Second Doctor retained his memory of the event, as per Katarina's last request. (AUDIO: Daughter of the Gods)