Omar Mateen, who perpetrated Sunday’s attack at a gay nightclub in Orlando, killing more than 50 persons, and injuring dozens others, pledged allegiance to the Islamic State (IS) during a 911 call he made during the incident. As in the San Bernardino incident in December 2015, carried out by an IS-inspired coupled, the quasi-state’s terror operations outside its core bases in Iraq and Syria are foretelling.

Against this backdrop, an analysis of IS terror operations outside its core bases in Iraq and Syria is foreboding. This is particularly so as the two-year milestone of the self-declared caliphate occurs on June 29th. Such anniversary dates are often marked by particularly vicious terror incidents. This is especially so when undertaken on behalf of jihadist groups, particularly during the Ramadan, which runs this year during June and early July.

Since the establishment of the IS, the group’s cells and those directed and inspired by the entity have claimed some 100 terror attacks in over twenty countries, resulting in more than 1,450 deaths and 2,000 injuries. Among the nations that have experienced the most incidents include Egypt (largely in Sinai), Yemen, and Libya—all where the IS has established “provinces” or wilayats. Other provinces in some ten countries range from Nigeria to Saudi Arabia and Afghanistan-Pakistan to Yemen. Attacks were likewise witnessed in other IS provinces, as well as in non-provinces worldwide (e.g., Western countries, Australia, and Asia).

Islamic State-led, directed, and inspired attacks included perpetrators comprising all races and genders, varied socio-economic backgrounds, and disparate paths to the cause, occurring online, offline, or both. The more sophisticated plots frequently included multiple operatives, who obtained the IS training, mostly in Syria, Iraq, or elsewhere (e.g., Libya). In some circumstances, the plotters were aided by a network of operatives who provided weaponry, training, funding, intelligence, procured transportation and safe houses, among other aid, whether before and after the attacks.

Hard and soft targets alike were featured in these incidents. Some incidents included coinciding or simultaneous assaults using varied modes of attack (e.g., gunfire, suicide bombings, and stabbings) against diverse targets (e.g., transportation, hotels, and religious institutions).

Among the bloodiest IS attacks during this period were:

• Three suicide bombers targeted the Brussels main international airport and subway killing 32 persons in March 2016.
• An armed attack in California resulted in 14 deaths during December 2016.
• Gunfire and suicide bombings at multiple targets in Paris and twin suicide bombings in Beirut caused 132 and 43 deaths, respectively, in November 2015.
• The bombing of a Russian passenger plane from Egypt (Sinai) to Russia and suicide bombings in Ankara killed 224 and 102, respectively, during October 2015.
• A lone gunman massacred 39 beachgoers in Tunisia in June 2015.
• A suicide bombing at Shiite mosque in Saudi Arabia killed over 30 during May 2015.
• Suicide bombings at Shiite mosques in Yemen caused more than 130 deaths in March 2015.

Besides successful IS-led, directed, and inspired attacks during the past two years, plots were derailed in the U.S., U.K., Russia, Saudi Arabia, and elsewhere. These planned incidents were undermined due to a combination of factors, ranging from gaps in an operative’s training or resolve to strong intelligence and police work, tips from the public, and interference from witnesses while attacks were underway.

The specter of the IS threat is particularly strong in Europe. In June 2016, German authorities disclosed that an Islamic State (IS) cell trained in Syria and already in Europe planned multi-prong terror attacks involving suicide bombers and automatic weapons in Dusseldorf. That plot is one of 120 Syrian-linked terror investigations taking place in Germany. Likewise, that month, Belgium’s Deputy Prime Minister projected that 100 returning foreign fighters may be planning terror incidents there.

Some 2,000 returning European fighters are unknown to authorities and may return to their home countries or third-countries to launch attacks. In addition, there are apparently several hundred IS-linked foreign fighters who are trained to conduct attacks internationally. The 5,000 IS-connected foreign fighters in Libya may have a simpler route into Europe than those based in Iraq and Syria.

Many of the European operatives in the November 2015 Paris and March 2016 incidents were believed to have trained with the IS in Syria. The heightened flow of Iraqi and Syria refugees across the Middle East, Europe, and beyond, has also contributed to the capacity of the IS to inject its personnel into target countries. This month, FBI Director James Comey voiced new concerns about the prospect of returning foreign fighters undertaking attacks in the United States.

Reports of IS-linked terror training camps in Bosnia, Kosovo, Belgium, and elsewhere in Europe portend the threat in Europe will not dissipate in the near term. This concern was confirmed in the May 2016 U.S. State Department’s European-wide terror travel alert valid through the end of August, namely, “The risk of potential terrorist attacks throughout Europe, targeting major events, tourist sites, restaurants, commercial centers, and transportation.”

These developments come on the heels of IS spokesman Abu Mohammad al-Adnani’s May 2016 exhortation for the group’s supporters to conduct attacks in their home countries: “Truly, the smallest act you do in their lands is more beloved to us than the biggest act done here; it is more effective for us and more harmful to them.” In addition, al-Adnani expressed that despite prospective IS territorial losses in Iraq, Syria, and Libya, the entity would regroup, and utilize insurgent tactics against its enemies, as it had in the past.

The scope of future IS attacks outside of Iraq and Syria depends on a myriad of factors including the group’s success in: radicalizing and recruiting individuals globally; being able to send trained operatives abroad; overcoming coalition military efforts in Iraq, Syria, and beyond; evading robust intelligence and law enforcement community efforts worldwide; leveraging encrypted and cutting-edge technologies; undermining international cooperation; and weakening the anti-IS efforts of the private sector, non-profits, and non-governmental organizations.

The implications of IS planned and actual terror attacks, the foreign fighter issue, and the group’s ability to leverage sympathizers and operatives worldwide are troublesome and multi-level in scope. These circumstances are emblematic of the group’s global reach, aspirations, capabilities, and strategic goals to expand territorial control, increase terror attacks globally, and destabilize sovereign states near and far.

As a result, the world at large is forced to play a greater role in combating IS than it otherwise would envision. In doing so, countries increasing view the IS challenges as both internal and external risks, even contributing to aggravated sectarian tensions in democratic states. Global responses to the IS will continue to engender broad political, economic, social, and legal actions with multiple—sometimes contradictory—consequences.

Ultimately, global resolve and resources can significantly weaken the group at its base, instrumentalities abroad, and future aspirants. Yet, as anti-IS forces continue in their efforts, prospective IS-led, directed, or inspired terror attacks are anticipated for the foreseeable future, with the Orlando incident the latest carnage inflicted worldwide.

Dean C. Alexander is Director/Professor, Homeland Security Research Program, Western Illinois University (WIU), and co-author of The Islamic State: Combating the Caliphate Without Borders (Lexington, 2015). Frank Parenti, a U.S. Marine Corps veteran, is completing his degree at WIU.