Indonesia–Malaysia confrontation during 1962–1966 was Indonesia's political and armed opposition to the creation of Malaysia. It is also known by its Indonesian/Malay name Konfrontasi. The creation of Malaysia was the amalgamation of the Federation of Malaya (now West Malaysia), Singapore and the crown colony/British protectorates of Sabah and Sarawak (collectively known as British Borneo, now East Malaysia) in September 1963.
The confrontation was an undeclared war with most of the action in the border area between Indonesia and East Malaysia on the island of Borneo (known as Kalimantan in Indonesia). However, Sabah and Sarawak were ethnically, religiously and politically diverse and there was some local opposition to joining Malaysia that Indonesia attempted to exploit, with very little success.
The terrain in Borneo was challenging and there were very few roads, both sides relied on light infantry operations and air transport, although rivers were also used. There was almost no use of offensive airpower. The British and Malaysian Armed Forces provided a significant element of the effort with no small parts being played by the other member nations (Australia and New Zealand) from the combined Far East Strategic Reserve stationed then in West Malaysia and Singapore.
Initial Indonesian attacks into East Malaysia relied heavily on local volunteers trained by the Indonesian Army. The main military forces backing Malaysia were British and initially their activities were low key. However, the British responded to increased Indonesian activity by expanding their own. This included, starting in 1965, covert operations into Indonesian Kalimantan under the code name Operation Claret. In 1965 there were several Indonesian operations into West Malaysia, albeit without military success. By August 1966, following Indonesian President Suharto's rise to power, a peace agreement finally took effect as Indonesia accepted the existence of Malaysia.