Combined Galactic Resistance

The Combined Galactic Resistance, was an alliance headed by humanity to fight the Dalek invasion of the galaxy in a time period in the future relative to Clara Oswald's home time. They were known to the Daleks as rebels, (TV: Into the Dalek) and identified by the Time Lords as "anti-Dalek forces". (PROSE: Dalek Combat Training Manual)

Dating
The book The Secret Lives of Monsters stated the Resistance fought during "the height" of the Dalek Wars. (PROSE: The Secret Lives of Monsters) One historical account also held that the Resistance had operated during the height of the Dalek Wars, crediting their preparedness for denying the Dalek Empire an easy victory. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

By another account however, the Resistance had operated during the Great War, fighting alongside the Space Security Service and operating in the frontier worlds, managing to drive the Daleks out of the Hermenides Cluster. (PROSE: The Whoniverse) Rusty, however, had memories of events that followed the Last Great Time War, suggesting that he was from a later point in Dalek history. (TV: Into the Dalek)

The Good Dalek
After the Draconian Empire had fallen, the Resistance became the primary force against the Daleks. As the war ground on, Colonel Morgan Blue was ordered to capture a living Dalek. At the cost of three ships and over 800 soldiers, Blue succeeded, bringing the Dalek, later to be named "Rusty", to the Aristotle. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

As its crew reported, the Aristotle found itself in the Ryzak solar system, where they found a significant amount of Dalek activity. Staying on station, the ship stayed hidden and shielded in an asteroid belt, promising more information would be reported later. (PROSE: The Secret Lives of Monsters) The Aristotle was further crewed by Lieutenant Journey Blue, Kai Blue, Gretchen Carlisle, and Ross who attempted to dissect Rusty for weaknesses only to discover he was sentient and sought to destroy the Daleks. After the Twelfth Doctor had rescued Journey, the Resistance recruited his services to diagnose Rusty. (TV: Into the Dalek)

Once Rusty was repaired, he sent a distress call to a nearby Dalek flying saucer and went on a rampage, attacking the resistance fighters. Once the saucer arrived, the resistance fighters, led by Colonel Blue, fought off the Dalek attack, many being killed in the process. The attack was eventually ended when Rusty, now reformed as the first moral Dalek, called for the saucer to retreat, killed the Daleks already onboard the Aristotle and followed the retreating Daleks to continue his efforts against them. (TV: Into the Dalek) Thus, the crew of the Aristotle had claimed a rare victory against the superior Dalek forces. (PROSE: The Secret Lives of Monsters)

According to the historians, Rusty's change of heart was eventually discovered by Dalek High Command, and scared them enough that they called off their war efforts. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)