Soldiers of the Chinese Red Army training for fighting the Japanese invasion, 1937 -- Daily Lift #653
The photo was taken by American journalist Harrison Forman who went behind the lines several times to report on and serve with Chinese Communist forces before and during World War II.
To read more about his time with the Red Army during the final months of the war see: The Communist fight to liberate China, 1945 (theleftchapter.com)