Klemens von Klemperer, a refugee from Nazi Germany who wrote what is widely considered the seminal history of the movement among the country’s conservative elite to overthrow Hitler, died on Dec. 23 at his home in Easthampton, Mass. He was 96.

His death was confirmed by his son, James.

Dr. von Klemperer, an emeritus professor of history at Smith College, was one of a generation of refugee historians who helped lay the groundwork for modern German and European studies in the United States, a group that also included Hajo Holborn, Fritz Stern and Peter Gay.

A privileged child who came from a family of German bankers and industrialists, he had taken a leading role in demonstrations against Hitler as a student in Vienna before fleeing to the United States in 1938....