Operation Merdeka
Part of North Borneo dispute and Indonesia-Malaysia Confrontation
Philippine Navy patrol boat (BRP Quezon) approaching Sabah.
Date April 18, 1971 - March 5, 1974
Location Sabah, Tawi-Tawi, Basilan
Result Treaty of Port Moresby
Sabah ceded to the Philippines
Flag of the Philippines (navy blue).svg Philippines

Supported by:
Flag of the United States.svg United States military remnant

Flag of Malaysia.svg Malaysia

Before Federation:

  • Flag of Malaya.svgMalaya
  • Flag of North Borneo.svgNorth Borneo
  • Flag of Sarawak.svgSarawak
  • Flag of Singapore.svgSingapore
  • Flag of Brunei.svgBrunei
  • Flag of the United Kingdom.svgUnited Kingdom (British Forces Command)
  • Flag of Australia.svgAustralia
  • Flag of New Zealand.svgNew Zealand
Flag of Indonesia.svg Indonesia
Commanders and leaders
Flag of the Philippines (navy blue).svg Ferdinand Marcos

Operation Merdeka (also called the Filipino Invasion of Sabah, Philippine Invasion of Sabah, Filipino-Malaysian-Indonesian conflict) was a military operation conducted by the Armed Forces of the Philippines in the "peacekeeping" or seizure of Sabah. While Filipino forces were initially successful in invading Sabah from Mindanao due to the disorganized Commonwealth-Malaysian forces and Indonesian troops, the battle became a war-of-attrition later on. It was only in 1974 that all three sides decided to solve the issue peacefully. As part of the Treaty of Port Moresby in 1974, Sabah was ceded to the Philippines that continues to be an issue over Malaysia-Philippines relations.


Sabah had been part of the Sultanate of Sulu in the early 14th century as prize to the sultan from Brunei for defeating enemy factions.

On January 22, 1878, the Sultanate of Sulu ceded or leased Sabah to British businessmen Alfred Dent and Baron von Overdeck, in which they would pay 5,000 Malayan Dollars per year.

The Madrid Protocol in 1885, signed by Great Britain, Germany, and Spain, relinquished all claims of the Spanish on North Borneo. The area was under the control of the British while the rest of the Sulu Archipelago was under the administration of the Spanish East Indies (which controlled the Philippine Islands, the Caroline Islands, and the Marianas Archipelago).

In 1898, the Philippine Islands was ceded to the United States in accordance to the Treaty of Paris - signed after the Spanish-American War. Initially, the treaty lines did not include North Borneo. In August 20, 1899, the Kiram-Bates Treaty acknowledged that sovereignty of the U.S. over Jolo and its dependencies. From the early 1900s to the 1930s, the British continued to pay lease. Sabah was occupied by the Japanese during World War II. Following the end of the war, the British annexed Sabah on July 10, 1946 - six days after the Philippines became independent from American rule. The Philippines and the United Kingdom, as well as the Federation of Malaya (later Malaysia) continued to dispute over Sabah up until the years before the Great Nuclear War. Just months before World War III, the heirs of the Sultan of Sulu ceded all rights, titles, dominion, and sovereignty of Sabah to the Republic of the Philippines.

The Great Nuclear War of 1962 made the Sabah issue temporarily forgotten by the Philippine government. It was only revived when Ferdinand Marcos won the Presidential elections against Diosdado Macapagal. Under Marcos, the country began manufacturing arms, weapons, and vehicles; either both Philippine-made or reversed-engineered from American military hardware left in the country. He also trained several Filipino Muslims for covert action in Sabah to prepare for Operation Merdeka, the codename for the Filipino invasion of Sabah.


The first phase of the invasion took place at midnight. The Philippine Air Force fighter jets buzzed Malaysian positions on Sabah. The Philippine Navy also bombarded the coast of Sabah. This was followed by an amphibious invasion from LCS, LCUs, and LVTs coming in from Basilan and Tawi-Tawi. Since the attack took place on midnight, Malaysian forces were caught off guard. Philippine Marines and Army troops quickly advanced throughout Sabah. Once the troops marched in to Kota Kinabalu, the Philippine flag was planted on its city hall. That morning, Malaysian citizens woke up to Filipino troops on their land.

In an attempt to buy the loyalty of the locals, the Filipinos installed a leader coming from the Sultanate of Sulu. This ensured that the locals will not poise a resistance.

Nonetheless, battles with Malaysian and Commonwealth forces continued as they staged hit-and-run attacks on the Filipinos. Indonesia, which previously supported the Philippines in its claim towards Sabah, also clashed with Filipino troops as communications broke down. Majority of Sabah was occupied by the Philippines but Malaysian, Commonwealth, and Indonesian troops continued operating in the rural areas of the island. This would continue until the Treaty of Port Moresby signed on March 5, 1974.


The Treaty of Port Moresby ensured that Indonesia would recognize the formation of Malaysia and that Malaysia, Indonesia, Brunei, the remnant UK forces, Australia, and New Zealand recognize the Philippines' sovereignty over Sabah. This would cause cold diplomatic relations for the Philippines and its neighbors. It also antagonized the SEATO alliance, since Filipino soldiers clashed with Australian, British, and New Zealander troops - all which are members of the intergovernmental organization.

The Philippines's diplomatic relations with Malaysia remained frosty until the late 1980s. The SEATO alliance was reorganized around the late 1990s, thus warming tensions over the members involved. SEATO then moved on how to deal with the spread of communism in Asia.

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