What led to increased tension between the United States and Japan in 1937?

Japan’s capture of Nanjing in 1937 was followed by the Nanjing Massacre, in which Japanese forces killed and abused large numbers of civilians and prisoners. News of these atrocities prompted outrage in the United States and increased tensions between the two countries. The Four Freedoms speech and Lend-Lease Act came later, during World War II.

AI-written and checked against the verified answer.