East West Street: On the Origins of “Genocide” and “Crimes Against Humanity” by Philippe Sands (Knopf, 448 pp. $32.50)

Polish-born legal scholars Rafael Lemkin and Hersch Lauterpacht, whose families were wiped out in the Holocaust, labored long and hard to bring about new categories of international crime. Lauterpacht’s principle of “crimes against humanity” was used at the Nuremberg trials to condemn 21 major Nazi war criminals. Though Lemkin’s concept of “genocide” was rejected at the trials, it was accepted later on. Philippe Sands, an international lawyer and professor of law at University College London, describes how these concepts became a staple of international law—and why they were necessary.

The aftermath of World War I had witnessed the rise of xenophobic nationalism attending the creation of new states in Europe. In its efforts to protect minorities in these entities, the League of Nations in 1919 required new states such as Poland to accept the provisions of a Minorities Treaty, conferring basic rights on all inhabitants without distinction of birth, nationality, language, race or religion.

Still, anti-Semitism trumped those protections and, as Sands writes in his indispensable book, “international law offered few constraints on the majority’s treatment of minorities and no rights for individuals. Each country was free to treat those who lived within its borders as it wished.” For example, the Nuremberg Laws of 1935 and Kristallnacht may have appalled many outside of Germany, but they did not violate international law.

Change was implemented only after World War II and the Nazis’ persecution of non-Aryans. Lemkin and Lauterpacht were both born in the city of Lvov (which today is Lviv in Ukraine) and both their families were murdered during the administration of Hans Frank, who became the head of Lvov’s general government following the Nazi conquest in 1939. The Nuremberg trials used Lauterpacht’s concept of “crimes against humanity”—which refers to the killing of individuals on a large scale—to convict Frank, but rejected Lemkin’s concept of “genocide”—which refers to the destruction of groups.

Lauterpacht and a number of American judges believed that emphasizing genocide might weaken the conviction that it is already a crime to kill one individual. It was best, Lauterpacht argued, to “put right” the relationship between crimes against humanity and genocide in favor of the former, Sands writes.

For his part, Sands describes how Lemkin attempted to convince the Nuremberg prosecutors that genocide “was the proper term to describe the defendants intent to destroy nations and religious groups.” He argued that “lesser terms like mass murder or mass extermination were inadequate because they were incapable of conveying the vital elements of racial motivation and the desire to destroy an entire culture.”

In December 1946, Lemkin’s lifelong work was vindicated when the United Nations General Assembly voted to affirm that “genocide is a crime under international law.”

Jack Fischel is author of the Historical Dictionary of the Holocaust.