Executive Summary


Coordinated suicide bombings staged by Islamic State (IS)-aligned Jamaah Ansharut Daulah (JAD) extremists in Indonesia's East Java Province, May 13-14 indicate an increasingly capable IS-linked network in the region. The recent incidents, which came only days ahead of the Islamic Holy Month of Ramadan, also highlight a broader IS trend of relatives jointly engaged in suicide attacks - a novel development in Indonesia. In response to the attacks, security forces launched a massive crackdown on suspected IS sympathizers throughout the country, while legislators in Jakarta expedited passage of overdue revisions to Indonesia's 2003 anti-terrorism law. New legal justification and a renewed perception of the terrorist threat suggests a prolonged crackdown will take place. Counterterrorism operations will almost certainly lead to highly visible, and possibly disruptive security measures in many major population centers and popular tourist destinations throughout the country in the coming months.

Key Judgments

  • The recent attacks in Surabaya showed a level of tactical and technical proficiency rarely demonstrated by decentralized terrorist cells, suggesting a connection between local extremist elements and experienced IS-aligned militants in the region.
  • The use of families, including women and children, in terrorist attacks could signal an evolving trend, which will likely pose fresh challenges for Indonesia's security forces, who will have to refine their own tactics to counter emerging threats.
  • The attacks will likely lead to a prolonged crackdown on suspected IS sympathizers throughout the country.

Family-executed Attacks

Members of JAD in East Java Province carried out a series of bombings that targeted three churches and a police headquarters in Surabaya, May 13-14. The attacks came ahead of the Islamic Holy Month of Ramadan and may have been launched in retaliation for the arrest of prominent IS supporter and cleric, Aman Abdurrahman, and East Java's JAD leader, Zaenal Anshari. In the bombings, the attackers deliberately employed their own children, who were used both as assailants and, likely unwitting, accomplices to their parents. In total, at least five adults and four children carried out the suicide attacks in Surabaya. Three other children related to the attackers were also killed in the explosions. The blasts killed at least 12 civilians and injured at least 46 others, including four police officers.

The first attacks occurred early May 13 when a husband and wife and their four children each detonated improvised explosive devices (IEDs) in quick succession outside of the Roman Catholic Church of Santa Maria Tak Bercela on Jalan Ngagel Madaya, the Diponegoro Indonesian Christian Church on Jalan Raya Diponegoro, and the Surabaya Center Pentecostal Church on Jalan Arjuno. All six attackers were killed instantly. Two other IEDs were found outside the Pentecostal Church but were reportedly disarmed by security forces.

In what appears to be a related incident the same day, another militant died when an improvised explosive detonated inside the Rusunawa Wonocolo apartment complex in Taman, Sidoarjo Regency, on Surabaya's southern outskirts. The man's wife and oldest son were also killed in the explosion, while the extremist's three other children sustained injuries in the blast.

On May 14, two more attackers, a husband and wife, detonated explosives mounted on motorcycles at the Jalan Sikatan entrance to the police headquarters in Surabaya's South Krembangan District. The attackers drove up to the checkpoint with their three children on the backs of the motorcycles before simultaneously triggering their IEDs. Four of the five family members were killed, while a daughter was severely injured.

Elsewhere, militant groups have used women and children as suicide bombers in the past, but the use of entire families in the Surabaya attacks signals an evolving trend in Indonesia. Militant groups who have sanctioned such attacks capitalize on the fact that women and children often face less scrutiny from security forces, and in some cases, enjoy relatively unfettered freedom of movement, which means attackers are less likely to be detected in the final stages of an operation. However, suicide attacks carried out by women and children appear to be more common in regions where militant groups control territory, or at least in areas where they maintain a strong network capable of vetting, recruiting, or otherwise indoctrinating, and training attackers and providing close oversight of the attacks themselves. IS does not control territory in Indonesia, but the attacks in Surabaya may be indicative of a growing and more capable network of IS-aligned fighters in the country.

Islamic State's Claim of Responsibility

Indonesian authorities have blamed JAD for the attacks in Surabaya, but IS quickly claimed responsibility for the May 13-14 bombings. The degree to which IS leadership was involved in the planning, funding, and execution of the attacks remains unclear. Links between central elements of IS and decentralized attackers are often minimal, sometimes little more than a single text or email exchange between an IS handler or propagandist, and the attackers. However, the fact that IS' claims were released within hours (rather than days) of the attacks may suggest a closer connection between the attackers and an IS propaganda wing. Additionally, statements made by Indonesian police officials, as well as some of the tactics/techniques employed by the attackers, are possible indicators of a deeper and more nuanced link between the perpetrators and seasoned IS-aligned operatives in the region.

Indonesia's Returning Fighters

The danger posed by seasoned IS fighters returning to their home countries is certainly real, but it remains to be seen how this threat will manifest itself on a broad scale. Approximately 700 Indonesian nationals are believed to have traveled in recent years to IS-controlled territory in Iraq and Syria, and dozens more were rumored to have joined smaller IS affiliates in the southern Philippines. It is unclear how many remain, or have been killed, in IS-controlled territory, and similarly unclear how many may have returned home. However, before the recent overhaul of the anti-terrorism law, Jakarta's policies regarding returning IS fighters were lax compared to other countries that aggressively prosecuted known IS sympathizers. Therefore, the likelihood that fighters fleeing battlefields in Iraq, Syria, the Philippines, and elsewhere have returned to Indonesia is high. Veteran IS fighters in Indonesia who remain loyal to the caliphate might try to disperse, establish support networks and operational cells, and attempt to recruit, train, and "deploy" local sympathizers. Even a small cadre of seasoned IS fighters could greatly enhance the operational capabilities of the existing extremist networks throughout Indonesia. The Surabaya bombings might be an indicator that this dynamic is starting to take shape.

Signs of Increasing Capability

IS has proven adept at inspiring decentralized sympathizers to wage violence on the group's behalf, but many attacks launched by IS' outlying supporters, while certainly impactful and sometimes deadly, are often rudimentary vehicular assaults or stabbings. When outlying cells of untrained sympathizers attempt more sophisticated attacks with explosives and firearms, the skills gap is often very apparent to the trained observer. The Surabaya bombings, on the other hand, were well coordinated, and displayed measures of proficiency not commonly exhibited by independent sympathizers. The level of coordination, and the attackers' "success rate" with very volatile explosives suggests, to a degree, the involvement of well-trained militants. It is possible that the IEDs employed against all four targets were built by seasoned fighters who likely had opportunities to hone their bombmaking skills in active conflict zones. All of the IEDs employed contained quantities of triacetone triperoxide (TATP), an explosive compound popular with insurgent groups and their sympathizers, as it can be produced with easily-sourced materials. However, the compound is very unstable and, absent appropriate safeguards, is known to detonate prematurely. Given that all of the IEDs employed in the attacks targeting the three churches and the police station, appeared stable, seemingly easily transportable, and reliable, it is extremely unlikely that amateur IS sympathizers with only a cursory understanding of explosives constructed the devices.


Since the Surabaya bombings, officials in Jakarta have overhauled Indonesia's dated anti-terrorism policies, and security forces will almost certainly continue to ramp up pressure on known and suspected IS sympathizers nationwide. However, the level of coordination and sophistication exhibited in the Surabaya bombings could be indicative of a deeper network of seasoned IS fighters in Indonesia, which will present a new set of challenges for the country's counterterrorism forces. The attacks will likely inspire other IS supporters to act independently, and an uptick in attempted rudimentary attacks is likely. However, an increase in complex, coordinated, and sophisticated attacks executed by more capable cells operating with direct guidance from IS-aligned fighters acting as handlers and trainers is also possible. Religious minorities and security forces will likely remain prime targets, but attacks targeting major commercial centers, popular tourist destinations, and transport hubs cannot be ruled out.

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