second sino-japanese war
The Second Sino-Japanese war, referred within China and Taiwan as "War of Resistance" and in Japan as "China-Japan war", was a war between the Kuomintang-led Republic of China with Communist China assistance and the Empire of Japan. The war began on 7 July 1937 when Japan invaded Manchuria, and was arguably the start of World War II. The war, and World War II, ended with the Japanese surrender at the end of World War II on 2 September 1945.
The war is a result of an escalation of Imperial Japan's ambitions in the east Asia according to the so-called "Greater East Asian Co-Prosperity Sphere" policy. While the war caused various warlord factions participated in the Chinese Civil War to temporarily unite in effort to defend the country, the ill-equipped Chinese forces suffered massive losses due to their dated equipment, though not without stalling the Japanese advance and inflicting large amount of casualties as well. In total, between 15 to 21 millions people died during the war, making it the second deadliest war in the 20th century.
The war is also infamous for numerous atrocities committed by the Imperial Japanese Army, in particular after the battle of Nanjing. The atrocity ranges from mass rape, indiscriminate mass killing, forced labor, usage of conventional and chemical weapons against civilians, and much more. Due to the modern Japanese government upheld the policy of "don't deny, don't admit" to not comment anything about the war, it still remains contentious issue between China and Japan (and Taiwan to an extent) to this day.
In Manchuria, Japan set up a puppet state called Manchukuo, while in Inner Mongolia their puppet state in the Mongol United Autonomous Government had established a new government in the form of Mengjiang (also known as Mengkukuo in the West).