Have foreign invaders been to Qinghai Province?

Military forces did not enter, but a large number of missionaries were active in Qinghai in modern times. They must have infiltrated politics, religion and culture. In addition, in modern times, foreign missionaries stole and smuggled a large number of ancient books and historical relics found in Dunhuang, which caused great cultural losses to China. At that time, their way back and forth should be through Qinghai.