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.