- The Konfrontasi was an “undeclared war” fought between Malaysia and Indonesia. The conflict started when Malaysia, consisting of Malaya, Sabah, Sarawak, and Singapore, was formed on September 16, 1963. Indonesia under President Sukarno was vehemently against the formation of Malaysia, which Sukarno saw as a British strategy to contain Indonesia’s geopolitical ambitions in the region (the Philippines was also against the formation of Malaysia but apart from braking off diplomatic relations did not resort to the use of military means). Sukarno launched a “Ganyang Malaysia” or “crush Malaysia” campaign, initially using political, economic, and propaganda means. When these actions failed, he decided to launch military attacks against Malaysia.
Maybe you knew about it but it's new to me.