 Conflicts between KMT and CPC were still common during the war, and documented claims abound of CPC attacks upon the KMT forces and vice versa.While the KMT army sustained heavy casualties fighting the Japanese, the CPC expanded its territory by guerrilla tactics within Japanese occupied regions, leading some claims that the CPC often refused to support the KMT troops, choosing to withdraw and let the KMT troops take the brunt of Japanese attacks.Japan surrendered in 1945, and Taiwan was returned to the Republic of China on 25 October of that year.