Rutan-Sontaran War

The Rutan-Sontaran War between the Rutan Host and the Sontaran Warburg lasted for millions of years across Mutter's Spiral.

Origins of the War
The Sontarans, at that stage not yet a species of clones, but already, according to the Doctor, a "fierce, martial race", began to sweep over Mutter's Spiral. Only the Rutans stopped them. Reacting to this, the Sontarans re-engineered themselves into clones and began to war with them. (DWM: Pureblood)


 * The Doctor described the war as beginning in the 15th century, which contradictions evidence given elsewhere.

Events in the War
During the 12th century (DW: The Time Warrior) and the 1900s (DW: Horror of Fang Rock), Earth assumed strategic importance by one or the other of the sides, who tried to make the planet into a military base for their respective species.

In the 1980s, the Sontaran Warburg investigated the possiblity of using TARDIS-like time ships in order to win the war. (DW: The Two Doctors)

After solar flares devestated Earth, a Sontaran scout landed in hopes of exploiting the planet's strategic importance. (DW: The Sontaran Experiment)

Involvement of Gallifrey
Though the Sontaran Linx, in the 12th century, merely considered the invasion of Gallifrey as a speculative possibility (DW: The Time Warrior), the Sontarans, in concert with the Vardans did invade, until beaten back by then-Lord President the Doctor. (DW: The Invasion of Time)

During another period of Time Lord history (whether before or after this time, we do not know), the Warburg and the Rutan Host convened on Gallifrey for peace negotiations. (PDA: The Infinity Doctors).