Shang Gyaltsen went to Tang China in 783, to meet with Chinese general Zhang Yi, and swore an oath of friendship between the two states.
Shang Gyaltsen sent 20 thousand men to help Tang China, but before they reached Chang'an, Zhu Ci was killed by his general and the rebellion was quickly put down.
Then Shang Gyaltsen sent another mission to China, asked Dezong to fulfill the promise, but was refused because the two places were both strategic strongholds and the Tibetan troops had never actually helped them.
He sent troops to invade China, sack Yanzhou (鹽州), Xiazhou (夏州), Yinzhou (銀州) and Linzhou (麟州), threatened to Chang'an.
Tsepangsa was the most important supporter of Bön, so, the king drifted apart the queen's clan, prohibited them from taking part in political affairs, and sent dbu ring, who was Shang Gyaltsen's son, to guard the palace gate.