LOCATION OF UNIT 731

Unit 731 in Harbin
Unit 731 was located in Pingfang, Harbin
What was Harbin?
Harbin was built in the late nineteenth century as part of the Russian Empire’s colonizing effort. In 1896, China sold Russia the right to build the Chinese Eastern Railway across Manchuria, from the city of Chita in Eastern Siberia to the city of Vladivostok, an important Pacific port for the Russian Empire.
This made Harbin an easily accessible hub especially for an operation like Unit 731. 
Related Book

Unit 731- The Forgotten Asian Auschwitz

The Japanese invasion of China during the Second Sino-Japanese war has left a strong legacy of hate and disgust among many Chinese today. Much of the atrocities committed by the Japanese are now known to most historians. By far, the most despicable and forgotten act against humanity committed by the Imperial Japanese government was its covert biochemical weapons program. Euphemistically labelled as the "Epidemic Prevention and Water Purification Department" of the Imperial Japanese Army, the Japanese conducted a wide range of cruel and inhumane experiments on prisoners who were often innocent.