Originally referred to as the United Nations Intelligence Taskforce, executive producer Russell T Davies claimed in 2005 that the UN were no longer happy to be associated with the fictional organisation and the UN's full name could now no longer be used.However, the "UNIT" and "UN" abbreviations could be used as long as it was not explained what the letters stood for.
In "The Power of Three" (2012), Kate heads UNIT's scientific research department, which now has authority over the military branch.
In a 2014 interview with Doctor Who Magazine, script editor Terrance Dicks recalled that he was present at the "birth" of UNIT during the production of the Doctor Who serial The Invasion (1968).
He credited both scriptwriter and script editor Derrick Sherwin and producer Peter Bryant as having come up with the idea beforehand, claiming that they were testing the concept in The Invasion before it had become central to the show in the Doctor Who serial Spearhead from Space (1970).
The final appearance of UNIT during the original run of Doctor Who was the Seventh Doctor serial, Battlefield (1989).
From "The Power of Three" (2012), the first on screen appearance of UNIT in any Whoniverse media since the two-part Doctor Who special The End of Time in 2009–2010, UNIT has been shown to have been reorganised by Kate Stewart, the Brigadier's daughter.