There are 2 excellent books on how the Chinese saved their imperial treasures from the Japanese invaders.
They are The Odyssey of China’s Imperial Art Treasures by Jeannette Elliott with David Shambaugh and Fragile Cargo by Adam Brookes.
These 2 books cover different aspects of the story. Thus, both are highly recommended by me.
Elliott starts with how the Imperial collection was started from the Xia Dynasty to the Qing and ends with how the collection was saved from the Japanese and ended up in Taiwan.
This book was based on research from 1986 to 1996 by his late aunt who left an uncompleted manuscript.
Fragile Cargo zooms in with the coup by the Christian General who deposed Pu Yi from the Forbidden City and set up a committee to catalog and preserve all the treasures inside the Forbidden City.
The strength of this 2022 book is its focus on the years 1924 to 1951.