After Tridu Songtsen purged Gar clan, he was sent to the east border to defense against Tang China.
He invaded Liangzhou and put Changsong (昌松, in modern Wuwei) under siege in 700, in order to vanquish Tibetan troops led by the traitor Gar Tsenba, but was utterly beaten by Chinese general Tang Xiujing.
Tridu Songtsen died in 704 in 'Jang (Nanzhao), and Nepal and Se rib revolted.
Mongpoje was appointed as Lönchen to put down the rebellion, but he tried to overthrow the powerful empress regent Thrimalö.
He was captured and executed, his position turned to another general named We Trisig Shangnyen.