War crimes in Manchukuo were committed during the rule of the Empire of Japan in northeast China, either directly, or through its puppet state of Manchukuo, from 1931 to 1945. Various war crimes have been alleged, but have received comparatively little historical attention. Legal basis Although the Empire of Japan did not sign the Geneva Conventions, which have provided the standard definition of war crimes since 1864, the crimes committed fall under other aspects of international and Japanese law. For example, many of the alleged crimes committed by Japanese personnel broke Japanese military law, and were not subject to court martial, as required by that law. Japan also violated signed international agreements, including provisions of the Treaty of Versailles such as a ban on the use of chemical weapons, and the Hague Conventions (1899 and 1907), which protect prisoners of war (POWs). The Japanese government also signed the Kellogg–Briand Pact (1929), thereby rendering its actions in 1937-45 liable to charges of crimes against peace, a charge that was introduced at the Tokyo Trials to prosecute "Class A" war criminals. "Class B" war criminals were those found guilty of war crimes per se, and "Class C" war criminals were those guilty of crimes against humanity. The Japanese government also accepted the terms set by the Potsdam Declaration (1945) after the end of the war. The declaration alluded, in Article 10, to two kinds of war crime: one was the violation of international laws, such as the abuse of prisoners of war; the other was obstructing "democratic tendencies among the Japanese people" and civil liberties within Japan. In Japan, the term "Japanese war crimes" generally only refers to cases tried by the International Military Tribunal for the Far East, also known as the Tokyo Trials, following the end of the Pacific War. However, the tribunal did not prosecute war crimes allegations involving mid-ranking officers or more junior personnel. Those were dealt with separately in trials held in China and in the Soviet Union after the surrender of Japan. Revisionist historians have contested that such crimes occurred. Far-right nationalist groups in Japan have denied war crimes as "anti-Japanese propaganda" to place modern Japan in a negative light for political purposes. War Crimes Human experimentation Special Japanese military units conducted experiments on civilians and POWs in Manchukuo. One of the most infamous was Unit 731. Victims were subjected to vivisection without anesthesia, and were