73 1 Unit (73 1 Unit) is a secret biological and chemical warfare research and development unit of the Japanese Imperial Army, which conducted deadly human experiments during the Second Sino-Japanese War (1937–1945) and the Second World War. It is responsible for some of the most notorious war crimes committed by Japanese personnel. The official names of the Imperial Japanese Army are the Gendarmerie Political Department and the Epidemiology Prevention Research Laboratory, which were originally established under the leadership of the Imperial Japanese Gendarmerie, with the aim of developing weapons of mass destruction to deal with China's army and possibly the Soviet army.

The following is a Chinese introduction (not the English translation above):

73 1 Army is the alias of the old Japanese Army (Kwantung Army) epidemic prevention and water supply headquarters. This unit is led by Shiro Ishii, so it is also called "Ishii Unit". 73 1 Force is also the name of War of Resistance against Japanese Aggression (1937- 1945) and the secret military medical forces engaged in biological warfare, bacteriological warfare research and human experiments during World War II.

73 1 troops disguised as water purification units. The 73 1 troops set up their base in the bungalow area near Harbin in northeast China, which was then part of the Puppet Manchukuo. Some researchers believe that more than 10000 Koreans, Koreans and allied prisoners of war were killed in the test of 73 1 unit, but the exact number is still controversial.

The behavior of 73 1 troops was just one of many war crimes committed by the Japanese imperial army during its occupation of Manchuria (from 193 1 to the end of World War II 1945). During this period,150,000 people were civilians from China, North Korea, the Philippines, Indonesia and Myanmar.