After several field trips to Asia, he returned to Harvard, where he taught the university's first courses in Japanese and Chinese art.
Warner had found evidence that the caves were the object of vandalism by Russian soldiers and reached an agreement with the local people to purchase the frescoes and remove them in order to save them for posterity.
Today the caves in Dunhuang are favored as tourist stops to showcase the Chinese view that the Americans pillaged their heritage.
[citation needed] The museum's position is that since they have a bill of sale indicating that Warner legitimately purchased the artwork, they have no obligation to return them.
[citation needed] Warner's archaeological career was interrupted by the United States' entry into World War II and he became part of the Monuments, Fine Arts and Archives (MFAA) Section of the U.S. Army.
[12] He has been given credit by some for advising against firebombing and the use of the atomic bomb on Kyoto, Nara, and Kamakura and other ancient cities to protect cultural heritage of Japan.
However, Otis Cary has argued that the credit for sparing Japan's cultural heritage sites belongs not to Langdon but to the U.S. Secretary of War, Henry L.