The Earth Alliance was a political entity, centred on Earth, that was formed by the 22nd century and became the dominant form of human government in the Mutter's Spiral from at least the 36th century to several hundred years later. It was a more loose alliance of human colonies against common threats than the earlier and more politically integrated Earth Empire. (AUDIO: The Sirens of Time, Invasion of the Daleks)
Related entities
The Earth Alliance was formed before the Earth Empire was created, and existed after it had collapsed. It was also partly concurrent with the much later Second Great and Bountiful Human Empire, which had spread throughout three galaxies by the 42nd century, (TV: Planet of the Ood) as well as the Galactic Federation of which the Earth was also a member. (PROSE: Legacy, TV: The Curse of Peladon)
Organisation
The head of the Earth Alliance was called the Grand Administrator. Their seat was in Brunei. (AUDIO: Rule of the Eminence) During the Second Great Dalek Occupation, the President of Earth appeared to be the head of the Alliance, until Earth fell to the Daleks. (AUDIO: “Death to the Daleks!”)
Spacefleet was a military organisation affiliated with the Earth Alliance. (PROSE: Return of the Living Dad)
Earth Command was the military strategy centre of Earth forces in the 40th century. (TV: The Infinite Quest)
History
The Earth Alliance fought to defend human colonies from the Daleks in the 22nd century. (PROSE: GodEngine)
The Battle of Bellatrix took place in the mid-26th century. It was a battle between the Daleks and the Earth Alliance's Spacefleet at planet Bellatrix. (PROSE: Return of the Living Dad)
The Earth Alliance fought a war against the Eminence, (AUDIO: Destroy the Infinite, The Seeds of War) eventually emerging victorious. (AUDIO: Rule of the Eminence) During the war, the Celestial Intervention Agency took over and repurposed an Earth Alliance space station at the edge of the ten systems. (AUDIO: The Death of Hope)
In 3562, the Earth Alliance defeated the Knights of Velyshaa. (AUDIO: The Sirens of Time)
Carthedia was recorded as a member of the Earth Alliance but during the Eleventh Doctor's visit it was found to be more closely affiliated with the Dalek Foundation. (PROSE: The Dalek Generation)
It appeared to be the dominant political entity in Mutter’s Spiral at the time of the Second Great Dalek Occupation. It fought against the Daleks’ invasion for over a decade, with the Dalek Empire expanding through the galaxy. (AUDIO: Invasion of the Daleks, The Human Factor, The Fearless) Baspral joined with the Earth Alliance in facing a Dalek advance. (PROSE: The Inquisitor's Story) Eventually Earth itself fell to the Daleks forcing the President of Earth to surrender, leaving what remained of the Alliance under the leadership of Ernst Tanlee. Shortly afterward the Alliance was reorganised when Susan Mendes triggered a galaxy-wide slave rebellion, throwing the Dalek Empire into chaos and liberating numerous occupied worlds. (AUDIO: “Death to the Daleks!”) Kalendorf helped reorganise the Alliance as the Daleks retreated on every front and led Alliance forces to reclaim Project Infinity, which the Daleks had taken with the aid of a duplicate of Tanlee. The duplicate managed to lower the Alliance’s defences however, allowing the Emperor Dalek’s flagship to retake the Project. The Emperor used the Project to make contact with Daleks of a parallel universe who ruled their universe. The parallel Daleks instead judged the Daleks as evil and declared war on them, (AUDIO: Project Infinity) allying with the Alliance. Within approximately six years, the Alliance and the “Alliance Daleks” had driven the “Enemy Daleks” back to a small stronghold within the Sol system.
Over time, Commander Kalendorf and his agents Alby Brook and Mirana began to develop doubts about the Alliance Daleks and their leader, the Mentor. Reports suggested that they enforced peace and order with the same ruthlessness with which the Daleks from the primary universe subjugated and conquered. Several planets which refused to provide troops to the war effort were reduced to a medieval level, having had their whole industrial infrastructure destroyed. In a more extreme example, Emmeron, which had been embroiled in a nuclear war by the time that the Dalek War began, was reduced to a Stone Age level. These worlds came to be known as the Punished Planets. The actions of the Alliance Daleks led Kalendorf to conclude that they had merely swapped one dictatorship for another, outwardly more benign one, and that humanity should fight against these Daleks as well as their more outwardly evil counterparts. (AUDIO: Dalek War: Chapter One) Kalendorf made a deal with the Dalek Supreme for a true between the Alliance and Enemy Daleks and for the Alliance to turn on the Alliance Daleks. (AUDIO: Dalek War: Chapter Three)
After many years of war, the Mentor finally decided to withdraw her Daleks back to their universe, believing the war would result in nothing but eventual extinction of life in the galaxy. A fragile peace remained beteeen the Daleks and Earth Alliance, which the Emperor was plotting to overthrow. Before the Daleks could strike however, Kalendorf travelled to Earth and initiated the Great Catastrophe. (AUDIO: Dalek War: Chapter Four)