Lemkin's first encounter with the concept of intentional destruction of groups occurred in 1915 with the news of the Turkish slaughter of Armenians.  He was also deeply affected by Quo Vadis, Polish author Henryk Sienkiewicz's novel about the persecution of Christians in Rome by Nero (37-68 C.E.).  

In  his autobiography, Lemkin cited the novel as the source of his inspiration to protect minorities from persecution. He wrote:

"Here was a group of people collectively sentenced to death for the only reason that they believed in Christ. And nobody could help them. I became so fascinated with the story that I looked up all the similar instances in history…"

Later in life, he also used the 1933 slaughter of Christian Assyrians in Iraq and the centuries-long oppression of Christians in Japan as case studies for his work on the legal conception of mass murder.