The Empire of Japan committed war crimes in many Asian-Pacific countries during the period of Japanese imperialism, primarily during the Second Sino-Japanese and Pacific Wars. These incidents have been described as "the Asian Holocaust". Some war crimes were committed by Japanese military personnel during the late 19th century, but most were committed during the first part of the Shōwa era, the name given to the reign of Emperor Hirohito. Under Emperor Hirohito, the Imperial Japanese Army (IJA) and the Imperial Japanese Navy (IJN) perpetrated numerous war crimes which resulted in the deaths of millions of people. Estimates of the number of deaths range from three to 30 million through massacres, human experimentation, starvation, and forced labor directly perpetrated or condoned by the Japanese military and government. Japanese veterans have admitted war crimes and have provided oral testimonies and written evidence, which includes diaries and war journals. Airmen of the Imperial Japanese Army Air Service and Imperial Japanese Navy Air Service were not charged as war criminals because there was no positive or specific customary international humanitarian law that prohibited the unlawful conduct of aerial warfare either before or during World War II. The Imperial Japanese Army Air Service took part in conducting chemical and biological attacks on enemy nationals during the Second Sino-Japanese War and World War II. The use of such weapons was generally prohibited by international agreements previously signed by Japan, including the Hague Conventions (1899 and 1907), which banned the use of "poison or poisoned weapons" in warfare. Since the 1950s, senior Japanese government officials have issued numerous apologies for the war crimes. Japan's Ministry of Foreign Affairs acknowledges Japan's role in causing "tremendous damage and suffering" during World War II, especially during the IJA's entrance into Nanjing, during which Japanese soldiers killed a large number of non-combatants and engaged in looting and rape. However, some members of the Liberal Democratic Party in the Japanese government, such as the former prime ministers Junichiro Koizumi and Shinzō Abe, have prayed at the Yasukuni Shrine; this has been the subject of controversy, as the shrine honours all Japanese who died during the war, including convicted Class A war criminals. Some Japanese history textbooks offer only brief references to the war crimes, and members of the Liberal Democratic Party have denied some of the atrocities, such as government involvement in abducting women to serve as "comfort women", a euphemism for