What was the relationship between chinese communist nationalists and japanese?

The Japanese occupied Manchuria, and distracted the Nationalist, which enabled the communist to consolidate and unite.

Explanation:

In central China, at that time, the communists had created  15 rural bases and they developed a soviet government.

On November 7, 1931. the Jiangxi Soviet within the soviet regions, the communist leadership took over and reallocated land and in other ways joined the support of the poorer classes.

in 1932 around the areas of Shanghai ,The Japanese occupation of Manchuria and an ancillary localized war, preoccupied the Nationalists and allowed the communists a quick opportunity to enlarge and unite.

In late 1934, the Nationalists  forced the communist armies to retreat and abandon their bases.