Churchill's information about the mass executions which followed the German invasion came directly from a German source. Six weeks before on July 9 British cryptographers broke the "enigma" code used by Berlin to communicate with the Eastern Front. Regular reports from mobile killing squads (the Einsatzgruppen which Churchill called "Police-troops") gave detailed accounts and specific numbers of 'Jews' and 'Jewish Bolshevists' killed in mass at locations throughout the occupied territory of the Soviet Union.

Therefore when Churchill spoke of whole districts being exterminated and "methodical, merciless butchery," he had specific detailed knowledge of locations and magnitude of the ongoing crime being committed by Germany in Ukraine and Russia. Churchill could not reveal the extent of his detailed knowledge without undermining British intelligence, yet he had to say something about a crime being committed.

In the United States, one man who heard Churchill's speech by radio was Raphael Lemkin, a refugee Polish-Jewish legal scholar who had arrived from Europe only five months before in April 1941. Prior to coming to America, Lemkin lived in neutral Sweden where he closely monitored German occupation policies in his native Poland where his parents and family remained, as well policies in neighboring Norway and all of occupied Europe. Swedish travelers coming and going from Stockholm helped Lemkin to assemble a collection of publicly available German occupation laws and decrees which Lemkin analyzed in an effort to understand the pattern of the policies being implemented in Hitler's New Order in Europe.

From these documents Lemkin concluded that alongside the traditional war of armies, Germany was engaged in a war against peoples. To Lemkin the collection of occupation decrees demonstrated a Nazi policy aimed at nothing less than a demographic restructuring of the European population. Following the design set out in Mein Kampf, some groups would be encouraged to thrive, others to decline through depopulation over time and others would be targeted for destruction.

In Lemkin's native Poland, for example, the German occupiers had created a racial hierarchy in which so called "Aryan" peoples (ethnic German Volkesdeutshe) received the full food rations and were encouraged to have more children, even out of wedlock. Ethnic Poles and other Slavic groups were forcefully subjugated, their leadership and intellectuals sent to concentration camps or killed outright. The remander of the Slavic population was to survive on minimal rations only to the extent that their labor was needed by the dominant "Aryan" population group. The Jewish population, two million people including Lemkin's own family, was being exterminated. Extermination was accomplished by forcibly resettling the population in ghettos or camps where people died rapidly through slave labor, starvation, exposure and contagious diseases such as typhus - living conditions designed to cause their destruction through attrition.

From his collection of documents Lemkin did not have evidence of mobile killing squads or death camps. But he did not need such evidence to reach his conclusion. Direct killing as a method of causing mass death only began to be practiced by the Nazi occupiers in the latter half of 1941. At that time Lemkin was already beginning to understand that extermination was occurring through policies of systematic attrition. Nazi mass killing by means of gas chambers would only be a more rapid way of accomplishing what they had already been doing through such policies as forcible resettlement and discriminatory food rationing.

In the United States, Lemkin explained German occupation policies in lectures and later in his book, Axis Rule in Occupied Europe . In the book's preface dated November 15, 1943, Lemkin introduced his new word paralleling homicide, for the offense of exterminating human groups. Winston Churchill had called the offense, "a crime without a name. " Raphael Lemkin called it "genocide."