During the eve of World War II, KMM, Ibrahim Yaacob and his colleagues actively encouraged anti-British sentiments. The Japanese also aided KMM and financed Ibrahim Yaacob's purchased of an influential Malay publication called "Warta Malaya" in Singapore. By 1941, the British began observing the activities of KMM as they perceived KMM as a radical left-wing association. By the end of the year, Ibrahim Yaacob, Ishak Muhammad and many other KMM leadership were captured and imprisoned. KMM was severely weakened by the action taken by the British.