I've told you several times before that in my high school days I was taken part in an extra-curricular activity once or twice, watching the documentary film of Resistance War against Japan.  Attached below is a fragment of the film at:

https://www.ixigua.com/a6502220964921606669/?utm_source=toutiao&utm_medium=feed_stream#mid=4185637519

Please note the background music of the film is "義勇軍進行曲", and it indirectly testifies in 1944 when the film was produced, the marching song had been widely sung in China, I guess even Chiang Kai-shek would have sung it in public.  So let's sing it again, loudly. 

P.S. Just six years later, China and United Nations' army led by America vehemently fought each other in Korean War.  Friend or foe?  At least during WWII, China and America were allies to each other; at least even now they are not sworn enemies to each other like that of Sino-Japanese relationship.