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 between at least the 36th and 42nd centuries. It was a more loose alliance of human colonies against common threats than the 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)
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)
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)
The Earth Alliance also fought a war against the Eminence. (AUDIO: Destroy the Infinite)
It was the dominant Earth-based political entity at the time of the Dalek invasion of Vega VI and, subsequently, Mutter's Spiral itself in 4162. (AUDIO: Invasion of the Daleks)
The remnants of the Earth Alliance allied themselves with the parallel universe Alliance Daleks, as they came to be known, which declared war on the enemy Daleks and fought alongside the Earth Alliance. Within approximately six years, they had driven them back to a small stronghold within the Sol system.
Over time, Kalendorf, Alby Brook and Mirana began to develop doubts about the Mentor and the Alliance Daleks. Reports suggested that they enforced peace and order with the same ruthlessness with which the Daleks from the primary universe subjugate and conquer. 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, Emeron, 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)
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)
At some point, Baspral joined with the Earth Alliance in facing a Dalek advance. (PROSE: The Inquisitor's Story)