What events prompted the Allied leaders to seek a way to protect monuments and fine art during the war as noted in the nonfiction book, The Monuments Men?

As the war began, a soldier noticed the destruction of monuments in Africa and suggested that actions be taken to protect them. At Monte Cassino, an ancient monastery was destroyed in an attempted to remove German soldiers from its walls. The Germans were never inside the monastery. These events inspired allied leaders to find a way to protect these monuments as well as fine art.