What led to increased tension between the united states and japan in 1937?

The Nanjing Massacre led to the increased tension between the United States and Japan in the year 1937.  

The Nanjing Massacre constituted and event of mass murder and mass rap* committed by Japanese troops against the residents of Nanjing, which was the capital of the Republic of China, during the Second Sino-Japanese War.

The massacre spanned for six weeks starting on December 13, 1937, the day that the Japanese captured Nanjing.  

The Nanjing Massacre

Explanation:

The Nanking Massacre was a massacre that happened in 1937 in which the Japanese Army killed thousands in the Chinese city of Nanking, the city was also destroyed.

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