- Television: The Invasion, BBC1 (2nd November 1968)
When the alien Great Intelligence invaded London, its robotic Yetis were opposed by the British Army, who found themselves ill-equipped to cope with an extraterrestrial threat. The Intelligence was eventually repelled with the assistance of the Time Lord known as the Doctor, and Colonel Alistair Gordon Lethbridge-Stewart, one of the officers who had worked with the Doctor during the crisis convinced the British government and United Nations for the need to create UNIT (the United Nations Intelligence Taskforce), an international organisation equipped to protect mankind from such threats, whether they were alien or homegrown.
The Brigadier and The Doctor
Promoted to Brigadier, Lethbridge-Stewart was placed in charge of UNIT's British division, with UNIT itself headquartered in Geneva. One of UNIT's first cases saw them investigate suspicious activites at International Electromatics, a company which turned out to be assissting the Cyberman in preparing for an invasion of Earth. The invasion was thwarted by the fledgling UNIT with the help of the second Doctor once again. After the Doctor was forced to regenerate by the Time Lords and exiled to Earth he was reunited with UNIT and the Brigadier, who convinced him to stay on as UNIT's unpaid scientific adviser. Initially partnered with UNIT scientist Liz Shaw, and later Jo Grant, the third Doctor and UNIT would fight back invasions from Axos, attempts by mankind's predecessors, the reptilian Silurians, to reclaim the Earth, and many other threats, but the most troublesome villain to dog UNIT during these years was the Doctor’s fellow Time Lord known as the Master. After coming to Earth seeking to destroy the Doctor, the Master became allied with various aliens in his ultimate goal of universal domination and the death of the Doctor and his companion Jo Grant. Eventually UNIT captured the Master and kept him imprisoned within a castle on the coast for a short amount of time, but he eventually escaped. After the Doctor’s exile was ended by his people, during an adventure that involved all three of the Doctor's incarnations, his association with UNIT became more periodic; Jo Grant travelled with him through time and space for a while, before leaving to be replaced by Sarah Jane Smith, a reporter and the Doctor's first post-exile companion who wasn't a UNIT operative. Following his regeneration into the fourth Doctor, the Doctor's association with UNIT lessened further and eventually ended. Years later, the fifth Doctor reunited with the Brigadier, who had retired from UNIT and then suffered an incident in which he encountered his future self and suffered amnesia. By the time of the seventh Doctor, the now-elderly Brigadier had re-established connections with UNIT and worked alongside its new leader, Brigadier Bambera. In the 21st century, UNIT (now named the Unified Intelligence Taskforce, working under the department of Homeworld Security), worked with the tenth Doctor on several occasions, and a former companion of the Doctor's, Martha Jones, became a medical and scientific adviser for the organization. UNIT also developed a relationship with the secret organization known as Torchwood, at once point seconding Jones to work with Torchwood's Cardiff branch.