The Indonesia–Malaysia confrontation, also known as Konfrontasi, was an armed conflict from 1963 to 1966 arising from Indonesia's opposition to the formation of Malaysia, which combined the Federation of Malaya, Singapore, and the British colonies of North Borneo and Sarawak. The conflict was rooted in Indonesia's previous confrontations against Dutch New Guinea and its support for the Brunei revolt. While Malaysia received military aid from the UK, Australia, and New Zealand, Indonesia had indirect backing from the USSR and China, making this a chapter of the Cold War in Asia.

The bulk of the conflict took place along the border between Indonesia and East Malaysia on Borneo. The dense jungle terrain led to both sides conducting extensive foot patrols, with combat usually involving small-scale operations. Indonesia sought to capitalize on the ethnic and religious diversity in Sabah and Sarawak to undermine Malaysia. Both nations heavily relied on light infantry and air transport, with rivers being crucial for movement and infiltration. The British, along with periodic assistance from Australian and New Zealand forces, bore the brunt of the defense. Indonesia's infiltration tactics evolved over time, shifting from relying on local volunteers to more structured Indonesian military units.

By 1964, the British initiated covert operations into Indonesian Kalimantan called Operation Claret. That same year, Indonesia ramped up its offensives, even targeting West Malaysia, but without significant success. The conflict's intensity dwindled after Indonesia's 1965 coup, which saw Sukarno replaced by General Suharto. Peace talks began in 1966, culminating in a peace agreement on 11 August 1966, where Indonesia formally acknowledged Malaysia.