As ruler Changchub Gyaltsen was keen to revive the glories of the Tibetan Empire of Songtsen Gampo and assert Tibetan independence from the Mongol Yuan Dynasty and from Ming Dynasty China.
The Old Tibetan Chronicle says that Myang Mangporje advised Songtsän Gampo against attacking the Sumpa, who had been among his father Namri Songtsen’s feudatory states.
As ruler Changchub Gyaltsen was keen to revive the glories of the Tibetan Empire of Songtsen Gampo and assert Tibetan independence from the Mongol Yuan Dynasty and from Ming Dynasty China.
The records of the Tang Annals do, however, seem to clearly place these events in the reign of Songtsän Gampo for they say that in 634, Yangtong (Zhang Zhung) and various Qiang tribes "altogether submitted to him."