What's that George Clooney movie "The Monuments Men"? In WW2 they saved 5 million pieces of art that had been stolen by Nazis.

"Many were the product of looting by Adolf Hitler and the Nazis. Others had been legitimately evacuated from museums for safekeeping. Monuments Men oversaw the safeguarding, cataloguing, removal and packing of all works from all these repositories."

They had to make up all the procedures because no army had ever thought of saving cultural property in this way before.