IT was known as the undeclared war.
The Indonesian Confrontasi (Confrontation) began in 1963 to destabilise the new-formed Federation of Malaysia which came into being the same year.
As it had promised, the United Kingdom wanted to combine its former colonies in northern Borneo with the Federation of Malaya.
In 1961, the UK and the Malayan government agreed to form Malaysia with Sabah, Sarawak, Brunei and Singapore.
Indonesia and Brunei opposed the idea. During this time, there were locals strongly against such a collaboration and they joined forces with their Indonesian counterparts to form the anti-Malaysia North Kalimantan People’s Army (Paraku) and Sarawak People’s Guerrilla Forces (PGRS) in the hope of unifying all the territories in Borneo to form an independent leftist North Kalimantan state.
The North Kalimantan (or Kalimantan Utara) proposal was seen as a post-decolonisation endeavour by local opposition to the formation of Malaysia.
Homegrown opposition in the Borneo territories was at that time based on economic, political, historical and cultural differences between the Borneo states and Malaya. The undeclared war ended in 1966.