Alternate History
I have envisioned an alternate history of what might have been if the Jabidah massacre never happened and so the following essay is entirely fiction so please don't take it seriously. Its just my impression of the point of divergence wherein the territorial dispute went hot.
What if the Jabidah Massacre never happened and the operational phase of the secret mission went to effect? Attacking Malaysia at this time may have been the perfect opportunity to do it. According to Whitman, "Marcos could not have chosen a more auspicious time to try and reclaim Sabah. Malaysia was only a fledgling state at that point, made even more wobbly by the secession of Singapore in 1965, two years after its independence from Britain. Too, Malaysia was embroiled in a border dispute with powerful Indonesia. And there was the Philippines' Sabah claim to boot. It was all that Malaysia could do to prevent itself from coming apart at the seams."
Imagine, 200 Jabidah commandos onboard several motorized bancas reached their respective assignment in various parts of the Sabah coastline. Many of these commandos have infiltrated various towns in the region. By this time, they have already urged the locals to rise up against the Malaysian authorities. Many of these commandos even claimed that they are liberating them from the "oppressive" government.
The main invasion force was preparing in Zamboanga City for an amphibious assault in Sabah. The elements of the newly-formed Philippine Marine Expeditionary Force (PMEF) and the war-decorated PEFTOK (Philippine Expeditionary Force to Korea), now designated as PEFTOS (Philippine Expeditionary Force to Sabah), have started its voyage to the battle front. The PEFTOS is composed of the 10th Battalion Combat Team (Motorized), 20th Battalion Combat Team (Leaders), 19th Battalion Combat Team (Bloodhound), 14th Battalion Combat Team (Avengers) and 2nd Battalion Combat Team (Bulldogs). They are the same battle-hardened units that saw action in the three-year Korean conflict.
In reality, the Malaysians were also misinformed in the diplomatic front because Foreign Affairs Secretary Narciso Ramos relayed President Marcos' message to Malaysian Prime Minister Tunku Abdul Rahman that the so-called 'military activity' was only a joint-military exercise by the Philippine Navy and Philippine Marines. Secretary Ramos reiterated that there is no such "provocative actions" made. Even though the Philippines broke diplomatic relations with her neighbor in 1963, the goverment tried to persuade the Malaysians that they were not thinking of some sort of "treachery."
X-day for Operation Merdeka was scheduled on July 17, 1968.
On July 16, the Sabah issue came to a precipitous height as angry mobs roamed the cities of Kota Kinabalu, Sandakan, and several small towns throughout the region. Many of the people, mostly of Tausug and Sama descent, burned the flags of their Malaysian rulers as they welcomed the Jabidah commandos as liberators. Caught by this whirlwind of events, the Malaysian armed forces were still in the peninsula and by this time they knew that the invasion was imminent.
The following day, the newly-commissioned Garcia-class frigates from the US Navy began softening the landing points of the PMEF and PEFTOS. The bombardment was so severe that not a single Malaysian soldier came up to opposed the amphibious assault.
The Philippine forces eventually reached Kota Kinabalu in less than a week and eventually combined with the Jabidah commandos. The Malaysian forces from the peninsula were on-route but it was harassed by the Philippine Fleet off the coast of Sarawak. Meanwhile, in the Philippine-occupied Sabah, the celebration was premature because some hard-line militias ambushed some of the Philippine forces that were posted in the outlying towns.
Indonesia, which earlier lost an undeclared war against Malaysia in 1962 to 1966, decided to align with the Philippines because both of them have scored to settle. In a secret deal, both countries will aid each other in the event of a Malaysian attack. The following day, the Indonesian Navy made a daring attack on the Royal Malaysian Navy's dockyards in Lumut at Perak province. Undeterred, the RMN was able to send some of its troops to Sarawak to face the PMEF but little did they know that the Indonesian Army was on its way to attack them from the rear.
The British, Australian and New Zealand governments, who are Malaysia's allies, saw such conflict to go out of hand. They raise their protests over the joint Philippine-Indonesian agression over Malaysia. But these diplomatic uproar fell on deaf ears. The Americans were also concerned about the situation because it is already embroiled in the conflict in Vietnam and that it is not prepared to go to another conflict in the region. But the Americans are obligated to help to defend the Philippines as part of their 1951 Mutual Defense Treaty and at the same time afraid to get into a conflict with its Cold War allies -- Great Britain, Australia and New Zealand. And so the Western governments have convened in Hawaii to discuss about the idea of not to support either of the belligerents. This decision means that there will be no active support given by the Americans to the Philippines and the British to the Malaysia. The war as to be fought between Malaysia, Philippines and Indonesia.
As the RMN attacked the Philippine-occupied Sabah, the IA attacked Sarawak on July 28, 1968. An effective rear-guard action by the RMA slowed down the Indonesia advance but effective pincer movement enabled the Indonesian armored division to punch through Malaysian lines and a crack Indonesian commando force managed to infiltrate into Sarawak under the cover of the thick rainforest of Kalimantan Timur. The bewildered RMN's supply lines were cut and on August 1, a joint Philippine-Indonesian force was paradropped into Bandar Seri Begawan that was aimed to breakout into multiple directions. The Brunei sultan Omar Ali Saifuddin allowed the troops to use his domain as their staging point as long as they will keep the peace in his land.
The Malaysians were in disarray as the Indonesian and Philippine troops were slowly converging from their positions and so on August 15, 1968, Malaysia surrendered. A peace treaty was signed in Cebu on September 9, 1968 with President Marcos, Indonesian leader Suharto and Malaysian Prime Minister Rahman. The Philippines annexed Sabah, Indonesia annexed southern Sarawak and northern Sarawak was subjected to sectors of occupation by both Philippine and Indonesian troops. As a reward for their support of the Philippine-Indonesian invasion force, Brunei was granted independence on September 10.