UNIT is a fictional military organisation from the British science fiction television series Doctor Who and its spin-offs Torchwood, The Sarah Jane Adventures, and The War Between the Land and the Sea. Operating under the auspices of the United Nations and initially led by Brigadier Lethbridge-Stewart, its purpose is to investigate and combat paranormal and extraterrestrial threats to Earth. Several UNIT personnel played a major role in the original Doctor Who series, and it was a regular feature from The Invasion (1968) until The Seeds of Doom (1976). The organization returned in the revived series, and has been led by Kate Lethbridge-Stewart since 2012.