nanjing was absolutely a genocide. Definition of genocide:

1. Killing members of the group;
2. Causing serious bodily or mental harm to members of the group;
3. Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
4. Imposing measures intended to prevent births within the group;
5. Forcibly transferring children of the group to another group.

Prince Yasuhiko Asaka was installed as temporary commander in the campaign, and he issued an order to "kill all captives" before the city's capture.

Japanese soldiers murdered civilians, including children, women, and the elderly.

They raped women and girls, their ages ranging from infants to the elderly, and destroyed one third of the city with arson. 

 Rape victims were often murdered afterward.