After slipping from the news headlines, the conflict and its aftermath in the southern Philippine city of Marawi has reappeared with the death of Omar Maute, co-founder of the Maute group, and Isnilon Hapilon, former Abu Sayyaf leader. In May, several hundred terrorists led by the Maute brothers and the Abu Sayyaf managed to seize the city. Despite some initial success, Philippine security forces continued to clash with a small group of entrenched terrorists until finally liberating the city in October.

The fighting resulted in a humanitarian crisis of tens of thousands of refugees forced to flee Marawi, the capital city of Lanao del Sur province (population 200,000) has been effectively destroyed by government aircraft in the effort to recapture it. This has caused major structural damage, with reconstruction costs estimated at $1 billion.

While it is true that the conditions around the seizure of Marawi were unique in terms of its scale and cross-tribal alliances (the Maute brothers were local Maranaos while Abu Sayyaf leader Isnilon Hapilon was an ethnic Yakan from Basilan province), it was not the first attempt by militants on the periphery to attempt a move into the heartland of Mindanao for "strategic depth" and access to greater resources.

The fact that 600-700 terrorists were able to coalesce essentially undetected is indicative of the armed forces' inability to counter this long-running insurgency.

The drawn-out battle and the fact that 600-700 terrorists (including dozens from Malaysia and Indonesia) were able to coalesce essentially undetected is indicative of the armed forces' inability to counter this long-running insurgency.

Many observers have expressed concern that Marawi's seizure in May will act as a "rallying cry" for terrorists in the region who have taken up the banner of ISIL. However the real risk is that the government botches the aftermath of the battle and "loses the peace."

For ASEAN as a whole, the issue is a much bigger one—terrorism will not be defeated in this region until Mindanao ceases to be a safe haven for regional militants. This will be achieved only when the island—which represents one quarter of the country’s population—is fully at peace and on a path to sustainable development and autonomy. For several decades Mindanao has been the place where terrorists in the region could shelter, train, and plan operations. Various local groups have harbored and supported these militants, ranging from established "liberation" movements such as the Moro National Liberation Front (MNLF) and Moro Islamic Liberation Front (MILF) to kidnap-for-ransom gangs like Abu Sayyaf. Mindanao also hosts the largest contingent of the communist New People's Army (NPA) and a plethora of private political armies.

Mindanao is rich in natural resources of all kinds but has historically been handicapped by poverty, poor governance, and a lack of economic investment and opportunity.

A comprehensive and sustainable solution to Mindanao’s instability can only be found by addressing four fundamental factors:

• Security reboot: Local security forces have never effectively dealt with the various armed groups on the island and an operational and strategic "reboot" is clearly needed to successfully do so. An overhaul of armed forces and national police, specifically in terms of counter-terrorism and maritime/coastal security, would assist the effort in gaining control of the problem.

Additionally, a focus on robust civil-affairs projects would assist in addressing the humanitarian crisis caused by the fighting. Capable units, such as the Special Action Force, require more advanced training and additional resources to address the problem. The United States and Australia are well-suited to assist the armed forces and police in these areas and have already offered assistance.

• Better growth: Although many observers both inside and outside the Philippines are celebrating the country’s record GDP growth, economic development has not been "equitable." It remains concentrated in southern Luzon and has not "trickled down" to the rest of the country.

Mindanao is rich in natural resources of all kinds but has historically been handicapped by poverty, poor governance, and a lack of economic investment and opportunity.

The government in Manila needs to ensure better-distributed growth, not just faster growth. In other words, the prospect of economic development is what is needed to successfully counter the appeal of ISIL, and disrupt recruitment of militants by domestic Islamist extremists that have adopted its ideology.

• Real autonomy: Former President Benigno Aquino re-launched a peace process to grant autonomy to key areas of "Muslim Mindanao"—an electoral and continuing promise made by President Rodrigo Duterte, who himself served as Davao city mayor for over 22 years before becoming president.

However, this process stalled after a botched police raid in 2015 to capture fugitive Malaysian bomb-maker Zulkifli, who was sheltering in Mindanao. Much of the separatist violence since then—including attacks in the cities of Zamboanga, Davao, and Marawi—is largely a result of the disrupted peace process, which has driven believers in a "Bangasmoro homeland" to see no other option but armed resistance.

The danger is that once aspirations for the creation of a "Southeast Asia caliphate" are destroyed and militant groups disperse from Marawi, targeting and attack patterns will reach a new, more unpredictable phase, with regional implications that extend far beyond the southern Philippines.

A revised draft of the Bangsamoro Basic Law (BBL), which implements the 2014 peace deal reached with the MILF, is now before Congress, but the danger is that it will languish there once more. The central government is otherwise distracted with political in-fighting, while the president for his part has yet to specify details of his own ideas for federalism, which would see greater autonomy (and revenues) granted to the regions. None of this bodes well for the peace process.

• ASEAN support: Finally, as Mindanao’s conflict has bled into parts of the neighboring East Malaysia’s Sabah and Sulawesi—where cultural and commercial connections have a long history—it is imperative to recognize the regional implications of the conflict.

Indonesian militants remain interested in plotting attacks on home soil, even as they have been drawn into the Mindanao front. However, once the militants in Marawi are over-run, there is a real risk of terrorism imploding once more. The danger is that once aspirations for the creation of a "Southeast Asia caliphate" are destroyed and militant groups disperse from Marawi, targeting and attack patterns will reach a new, more unpredictable phase, with regional implications that extend far beyond the southern Philippines.

The "greater Sulu" region is one of fluid marine borders (there are over 70 un-gazetted ports) and strong tribal and clan connections where maritime trade, piracy, raiding, and smuggling all have long traditions.

A large island afflicted by a coalescence of ethno-separatism, terrorism, narcotics smuggling, and criminality means that its neighbors will continue to bear the consequences of the negative side effects of its instability.

A large island afflicted by a coalescence of ethno-separatism, terrorism, narcotics smuggling, and criminality means that its neighbors will continue to witness, and on occasion bear the consequences of, the negative side effects of its instability (for example, the 2013 armed invasion of the town of Lahad Datu in Sabah).

The countries affected need to better coordinate their counterterrorism efforts and the Philippines should request assistance from Malaysia's and Indonesia’s police and security forces to end this regional threat.

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Dane Chamorro is a senior partner at Control Risks and a former resident of the Philippines.

Bill Dickey is a retired US Army colonel and former US Army attaché in Jakarta and defense attaché in Yangon.

This article was originally published by CSIS.

The views and opinions expressed here are those of the authors and do not necessarily reflect the official policy or position of the Pacific Council.