2001 Sontaran invasion of Earth

In 2001, the Sontarans invaded Earth, however they were defeated by the Earth Defence Force.

A day to come
The conflict (and some extent of its outcome) was seemingly known to Sontarans relative to the time prior to the invasion. When Group Marshal Nathan of the Tenth Sontaran Battle Brigade inexplicably boarded the Sixth Doctor's TARDIS with Turner to destroy the TARDIS with a vitrox bomb, they were lured to the TARDIS control room by the Doctor and Tegan. The Doctor and Gareth Jenkins, having laid a deadly trap for the Sontarans, along with Tegan, waited for their arrival. When the Doctor introduced Tegan and Gareth, Group Marshal Nathan identified Gareth's name belonging to that of the leader of the Earth Defence Force who thwarted the Sontarans' invasion in the future, and was happy that he had captured such a prize as their would-be enemy. While the Doctor suggested the names may have just been a coincidence, Nathan didn't want to take that risk, and so ordered his subordinate to kill Gareth; however Gareth sprung the trap that he had set, killing the Sontarans brutally with some soft of gas. However, their victory was small as the rest of the Tenth Sontaran Battle Brigade were massed outside the TARDIS. (HOMEVID: A Fix with Sontarans)

The invasion
The Sontarans invased Earth in 2001, but were defeated by the Earth Defence Force as led by one Gareth Jenkins. (HOMEVID: A Fix with Sontarans)