Brunei was supposed to join the Federation of Malaysia, which is a federation consisting of Malaya (itself a federation), Singapore, North Borneo and Sarawak. However, it faced a rebellion on its own front, the Brunei Revolt. read more
The status of Limbang as part of Sarawak has been disputed by Brunei since the area was first annexed in 1890. The issue was reportedly settled in 2009, with Brunei agreeing to accept the border in exchange for Malaysia giving up claims to oil fields in Bruneian waters. read more