The reason for the victory of the War of Resistance Against Japanese Aggression was the result of the combined action of many factors.
First of all, the Communist Party of China played a mainstay role in the War of Resistance Against Japan. The CPC's all-out anti-Japanese war line and protracted strategic policy pointed out the direction for the victory of the War of Resistance Against Japanese Aggression. The battlefield behind enemy lines led by the Communist Party of China and the frontal battlefield led by the Kuomintang cooperated with each other to form a strategic situation of jointly resisting the Japanese invaders.
Second, the great strength of the Chinese people was the decisive factor in the victory of the War of Resistance Against Japanese Aggression. The Chinese people showed great patriotic enthusiasm and tenacious fighting spirit during the War of Resistance Against Japan. They were not afraid of strong enemies, they were not afraid of sacrifice, and fought bravely to defend the motherland. The War of Resistance Against Japanese Aggression of the Chinese and the People's Republic of China was a war of resistance of the whole nation, and the people of all nationalities, classes, parties, and organizations, as well as overseas Chinese, all took an active part in the War of Resistance.
Thirdly, the sympathy and support of the world's anti-fascist forces was also an important reason for the victory of the War of Resistance Against Japanese Aggression. During the War of Resistance Against Japanese Aggression, many countries and peoples provided material and moral support to China. The United States, Britain, the Soviet Union and other countries provided China with a large amount of military and economic assistance, making important contributions to China's victory in the War of Resistance Against Japanese Aggression.
Finally, the injustice and aggressiveness of the Japanese aggressors were the fundamental reason for their defeat. The Japanese invaders committed heinous crimes in China, arousing great indignation and strong resistance among the Chinese people. The War of Resistance of the Chinese and the People was a just war, in which the righteous were helped by many and the unrighteous were helpless, and finally won the victory.
To sum up, the reason for the victory of the War of Resistance Against Japanese Aggression was the result of the combined effect of the mainstay role of the Communist Party of China, the great strength of the Chinese people, the sympathy and support of the anti-fascist forces in the world, and the injustice and aggressiveness of the Japanese aggressors.