In Shanghai, he met an old acquaintance, John Hadley Cox, a 34-year-old American who had worked for the Yale-China Association in the 1930s.
Mr. Cox was now a key officer in the Office of Strategic Services, the American military intelligence service that preceded the C.I.A. Even before the Japanese surrender in 1945, Mr. Cox had been sent to Shanghai to collect intelligence.
He was also an amateur historian and art collector. According to correspondence discovered by Professor Li, Mr. Cox asked to buy the silk manuscript after reading Mr. Cai’s book. The two struck a deal: Mr. Cox made a $1,000 down payment and promised $9,000 more upon resale.
Within days, Mr. Cox contacted another American military intelligence officer who flew the silk and other items to the United States, taking them through customs as Chinese antiques, “value unknown.”
It was not illegal in the United States at the time to import looted art, but China prohibited the export of excavated antiquities, which were considered state property.
“It’s fair to say it was smuggled out of China,” said Lai Guolong, a professor at the University of Florida who specializes in Chinese antiquities laws. “It’s just that China was too weak to do anything.”
In the United States, Mr. Cox — who went on to pursue research into ancient China and donated some of his other holdings to the Freer Gallery in Washington, and his alma mater, Yale — offered the ancient manuscript to numerous museums.