This group is also called Komunis or Malayan People Anti-Japanese Army (MPAJA). This group is the Communist Party of China. When Japan ruled Malaya, it mistreated the Chinese in Malaysia because of the Sino-Japanese War of 1937. So, this group organized against the Japanese. When Japan was defeated, the Communists occupied Malaya for 14 days. During this period, all Malays suspected of having ties to Japan were killed. Therefore, the British (the rulers at the time) regarded the Communists as murderers and the group was banned. Until finally, they returned to Japan

Taken from: History of Malaysia (Sejarah Melayu)