There was a recent article on the Diplomat that doesn't answer your question directly, but gives you a better context for the times: http://thediplomat.com/2014/09/the-ccp-didnt-fight-imperial-japan-the-kmt-did/

From 1937 to 1945, there were 23 battles where both sides employed at least a regiment each. The CCP was not a main force in any of these. The only time it participated, it sent a mere 1,000 to 1,500 men, and then only as a security detachment on one of the flanks.There were 1,117 significant engagements on a scale smaller than a regular battle, but the CCP fought in only one. Of the approximately 40,000 skirmishes, just 200 were fought by the CCP, or 0.5 percent.

By the CCP’s own accounts during the war, it barely played a role. Specifically, in January 1940 Zhou Enlai sent a secret report to Joseph Stalin which said that over a million Chinese had died fighting the Japanese through the summer of 1939. He further admitted that only 3 percent of those were CCP forces.