Taizong turned the proposal down. When the Tibetan emissary returned to Tibet, he informed Songtsen Gampo, falsely according to Tibetan historical sources, that Taizong was disposed to approve a dynastic marriage but changed his mind after hearing the Tibetans slandered by the Tuyuhun. It was said that Murong Nuohebo had visited Tang and was interfering, leading to Taizong's refusal. Songtsen Gampo, believing the report, attacked Tuyuhun in late 637 and early 638, capturing some of them and forcing the rest to flee north of Qinghai Lake.