Weytahn (Paan Mokar to the Vulcans) was the name of a planet that, in the 22nd century, was situated between the Vulcan system and the Andorian Empire. It was disputed territory of both powers, settled by Andorians in the 2050s who were then evicted by Vulcan forces in 2097.
In 2152, Andorian Commander Shran landed an occupation force on Weytahn, leading to hostilities between Andoria and Vulcan. The two sides agreed to have Earth Starfleet Captain Jonathan Archer negotiate an end to the conflict. (ENT episode: "Cease Fire")
The Vulcans eventually agreed to cede Weytahn to the Andorians. In 2154, Vulcan High Command Administrator V'Las created misinformation that Vulcan planned to retake Weytahn, in order to convince the Andorian Imperial Guard to redeploy their forces and leave Andoria open to invasion. (ENT episode: "Kir'Shara")
In the mirror universe, General Shran ordered all outposts on Weytahn destroyed, claiming the world was a rebel stronghold. In fact, there were no rebels on Weytahn, and the assault was carried out for propaganda purposes only. (ENT novel: Age of the Empress)