What Was Unit 731?

Unit 731 of many covert Imperial Japanese facilities specializing in biological and chemical warfare during World War II.
It was thought at the time, that Unit 731 was researching chemical compounds.
It was discovered that the primary research done there was to do lethal experiments on live human beings.
At Unit 731, they cultivated dangerous diseases, like the plague and then injecting it into unwilling test subjects.
The scientists then would study how the diseases would ravage the bodies of the victims.
Some of the prisoners were raped to see if the diseases were passed on to the babies.
They would frostbite testing, captives were taken outside and have various appendages into water, and allowing the limb to freeze. Once frozen, was struck with a short stick, ice was chipped away and the area doused in water. 
The effects of different water temperatures were tested by bludgeoning the victim to determine if any areas were still frozen. Variations of these tests in more gruesome forms were performed.
Over 3,000 men, woman, children and infants were killed.
During the final months of World War II, Japan planned to use plague as a biological weapon against San Diego, California.

The plan was scheduled to launch on September 22, 1945, but Japan surrendered five weeks earlier.

After the war the scientists were rewarded and welcomed into the United States to share their expertise.
Several former Unit 731 officials went on to have successful careers in medicine, academia and business.