The accession ceremony of the Zidanku Silk Manuscripts (Volumes II and III) is held at the Hunan Museum in Changsha, capital of central China's Hunan Province, Oct. 13, 2025. (Xinhua/Chen Zhenhai)

CHANGSHA, Oct. 13 (Xinhua) -- Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions.

The second and third volumes of the Zidanku Silk Manuscripts -- precious cultural artifacts dating back to the Warring States Period (475-221 B.C.) -- were on Monday officially repatriated to Hunan Province. They will be permanently archived in the Hunan Museum in Changsha, the provincial capital.

The manuscripts, which were unearthed from a Chu-state tomb by tomb raiders at the Zidanku site in Changsha in 1942, consist of three volumes: "Sishi Ling," "Wuxing Ling" and "Gongshou Zhan." They are a systematic record of astronomy, calendars, cosmology and military divination from China's pre-Qin period. The silk manuscripts, are the earliest examples of silk text discovered to date and the oldest classical Chinese book in the true sense. They were smuggled out of China in 1946.

At the accession ceremony of the Zidanku Silk Manuscripts (Volumes II and III) on Monday, National Cultural Heritage Administration (NCHA) head Rao Quan said that the return of the manuscripts is a significant achievement of years of Sino-U.S. cultural and museum cooperation, and an example for international cooperation on artifact restitution.

Through Sino-U.S. cooperation on the return of cultural property, the "Wuxing Ling" and "Gongshou Zhan" volumes were returned to China by the Smithsonian Institution's National Museum of Asian Art this year, arriving in Beijing on May 18.

Duan Xiaoming, curator of the Hunan Museum, said the return of the silk manuscripts will enable the Hunan Museum to integrate the returned volumes with its existing collection, which includes the only original fragment of the Zidanku manuscripts, as well as other Chu-state artifacts.

The returned manuscripts have undergone 14 days of environmental adaptation observation after their arrival in Hunan Museum on Sept. 10. Following a non-destructive evaluation, they are now stored in a temperature-controlled and humidity-controlled environment. A team of experts is scientifically researching a microbial disinfection plan and conducting simulation experiments to ensure that the sterilization process does not damage the material or ink of the manuscripts.

The Hunan Museum has also completed standardized imaging of all the silk manuscripts, discovering over 40 previously imperceptible ink characters on one piece of silk that had not fully separated. ■

Staff members prepare to conduct standardized image collection of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province, Sept. 11, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

This photo taken on Sept. 11, 2025 shows parts of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

This photo taken on Sept. 11, 2025 shows parts of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

This photo taken on Sept. 11, 2025 shows parts of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

Staff members transfer a box containing the Zidanku Silk Manuscripts at Changsha South Railway Station in Changsha, capital of central China's Hunan Province, Sept. 10, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

Experts verify the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province, Sept. 11, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

Staff members open the boxes containing the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province, Sept. 11, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

This photo taken on Sept. 11, 2025 shows parts of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

This photo taken on Sept. 11, 2025 shows parts of the Zidanku Silk Manuscripts at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Xue Yuge)

The accession ceremony of the Zidanku Silk Manuscripts (Volumes II and III) is held at the Hunan Museum in Changsha, capital of central China's Hunan Province, Oct. 13, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Chen Zhenhai)

This photo taken on Oct. 13, 2025 shows part of the Zidanku Silk Manuscripts on display at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Chen Zhenhai)

Journalists take images of the Zidanku Silk Manuscripts on display at the Hunan Museum in Changsha, capital of central China's Hunan Province, Oct. 13, 2025. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Chen Zhenhai)

This photo taken on Oct. 13, 2025 shows part of the Zidanku Silk Manuscripts on display at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Chen Zhenhai)

This photo taken on Oct. 13, 2025 shows part of the Zidanku Silk Manuscripts on display at the Hunan Museum in Changsha, capital of central China's Hunan Province. Two volumes of Chinese silk manuscripts dating back about 2,300 years have been returned to central China, 79 years after they were smuggled out of the country, through cooperation between Chinese and the U.S. cultural institutions. (Xinhua/Chen Zhenhai)