What is Unit 731?

Normally, when somebody talks about WWII, especially when someone talks about mass murders, genocides, and Concentration Camps we immediately associate it with Germany and Nazis. Most people wouldn't associate this with Japan. But the reality is that Japan commited horrible war crimes against humanity. For this purpose they used a division of the Imperial Army called Unit 731.

For those who don't know, Unit 731 was a special unit from the Japanese Imperial Army that was in charge of developing biological and chemical weapons. They tested this weapons performing horrible experiments with living people in "concentration camps" that were located in China. These experiments were considered-even in those days-unmoral and unethical by the international community. 

This unit was directed by General Shiro Ishi who personally conducted their operations. It is estimated that between 3000 and 12000 people were killed by  Unit 731 during its 10 years of activities, until the japanese surrender to the Americans in 1945. 

The Americans knew what was happening inside Unit 731's facilities. Nevertheless they helped them not to be trial in exchange for information obtained from their experiments. With this information, some of the most important medical advances were achieved. 

The question is:

The slaughter was worth? The end justifies the means? Would you do the same to save a person?