She was serving with Commander Shran when an Andorian invasion force landed on the disputed planet of Weytahn and occupied the Vulcan settlement. Shran insisted that Captain Jonathan Archer should be the one to negotiate a cease fire between the two enemies. Tarah objected to his attempts to negotiate with the Vulcans, as she believed that the Andorians should continue the fighting and reclaim the planet. Shran noted her suggestion, but proceeded with the negotiations.
Tarah decided to order the Andorians who wished to reclaim Weytahn by force to fire on the shuttlepod that was carrying Archer, Sub-Commander T'Pol and Ambassador Soval to meet with Shran. After they escaped from the crashed shuttlepod, the three were attacked by Andorian snipers, including Tarah who was sent to rescue them by Shran.
After Archer stopped her from killing Soval, Shran arrived. Tarah confessed to him that it was she who ordered the attack on the shuttle. She told Shran that there were more Andorians like her who would rather fight the Vulcans than negotiate with them. Tarah accused Shran of being a coward and traitor and begged him to redeem himself by killing Soval and continuing the armed conflict. He refused and had her arrested. (ENT: "Cease Fire")