Why did the Nanking Massacre happen?

Seventy years ago this December 13th, the Japanese Imperial Army began its seizure of Nanjing, the capital of the Republic of China. Japanese troops killed remnant Chinese soldiers in violation of the laws of war, murdered Chinese civilians, raped Chinese women, and destroyed or stole Chinese property on a scale that will never be known. The violence and destruction was extensive, despite the efforts of some Japanese to minimize the scale. We know this because there was a relatively large foreign community in Nanjing at the time that bore witness to the carnage. Other Japanese have themselves worked assiduously to reconstruct the historical record.

Explanation:

b) that he was not a free man

they remained in rural areas and worked at jobs such as lumbering or farming.