United Nations

The United Nations (UN for short) functioned as a coalition of Earth nations, which also created international campaigns and programs. The UN co-ordinated many of these efforts from its office in Geneva, Switzerland, the largest UN office outside of its New York City headquarters.

20th century
In the late 20th century, the UN put together the United Nations Intelligence Taskforce (later the UNified Intelligence Taskforce) to defend the Earth against threats such as the Great Intelligence. UNIT Central Control was placed in Geneva. (TV: The Invasion et al). This was done after a direct appeal by Alistair Gordon Lethbridge-Stewart. (PROSE: Who Killed Kennedy) UNIT's international status would allow to go over the head of British military figures (TV: The Invasion), but also meant the authorities didn't trust it. (TV: The Ambassadors of Death)

General Carrington advised the UN Security Council to coordinate a global nuclear assault on the Ambassadors' spaceship. The Council could not agree on how to respond, leaving Carrington frustrated. (TV: The Ambassadors of Death)

In the 1980s, the UN oversaw a space agency, International Space Command. (TV: The Tenth Planet)

In 1994, the UN's Security Yard gained its own military branch, UNISYC; it would squabble with other UN factions for alien weaponry in 1996. (PROSE: Interference - Book One)

21st century
During the 2000s, due to an unspecified incident, the UN possessed the launch codes for the United Kingdom's nuclear deterrent. (TV: World War Three) Due to a sharp increase in alien incidents, the UN increased funding for UNIT under a policy of "homeworld security". (TV: The Sontaran Stratagem) It also went into emergency session when faced with such apocalyptic events as the Moon heading towards Earth. (TV: The Lost Boy)

In 2007, UN troops were stationed in Turkey. (PROSE: Cat's Cradle: Warhead)

In 2009, the United Nations surrendered the Earth in the face of a massive Dalek invasion of Earth. (TV: The Stolen Earth)

During the Miracle Day phenomenon, China dropped out of the United Nations. (TV: The Gathering)

Later History
In later years of the 21st century, the United Nations might have replaced UNIT with UNISYC (PROSE: Alien Bodies) and/or PRISM (PROSE: The Indestructible Man). It might have transformed into a world government. (TV: The Enemy of the World, PROSE: The Indestructible Man)

Behind the scenes

 * After the broadcast of Aliens of London, it was announced that the United Nations were no longer happy to be directly associated with UNIT. The term "UN" could, however, be used as long as it wasn't stated what it stood for. Subsequent stories, UNIT's name has not been explained. Later it was shown to stand for Unified Intelligence Taskforce.