WASHINGTON—When Assistant Secretary of State David Stilwell instructed China’s ambassador that the Houston consulate ought to near within seventy two several hours, he shipped a similar message: Eliminate all Chinese army scientists now in the U.S.

The July 21 purchase on the scientists, which has not been beforehand described, was the fruits of months of rising issue in the Trump administration more than what U.S. officials depict as an intelligence-accumulating procedure aided by Chinese diplomats to acquire cutting-edge scientific investigate from American…