Libya: estimates vary; 5,000–6,500 (Feb. 2016, New York Times citing Pentagon officials) "about 5,000" (Feb. 2016, al-Jazeera citing "security analyst") "up to 6,500" (Feb. 2016, CNN citing "several U.S. intelligence officials")
Jordan: several thousand members of Salafi jihadist groups that have pledged allegiance to ISIL (Jordan Times, 2014) Several Jordanian jihadist ideologues have endorsed ISIL ISIL sleeper cells exist in the country (about 20 killed by Jordanian security forces, and many more arrested, from 2014 to April 2016) 2,000+ Jordanians became ISIL foreign fighters in Iraq and Syria.
Turkey: nearly 1,000 arrested by Turkish security forces in 2015
Their military is based on mobile units using light vehicles such as gun-equipped pick-up trucks (technicals), motorbikes and buses for fast advances. They also use artillery, tanks and armored vehicles captured from the Iraqi and Syrian Armies. ISIL also captured some aircraft, for example at Al-Tabqa Airbase, though they were inoperable.
ISIL's fighters are reportedly organised into seven branches: infantry, snipers, air defence, special forces, artillery forces, the "army of adversity", and the Caliphate Army. This force structure is largely replicated in each of its designated provinces, with the most skilled fighters and military strategists in each area serving in the special forces unit, which is not allowed to redeploy to other provinces. Parallel to this structure is the Caliphate Army, which is directed by ISIL's central command rather than its provincial leadership. Made up overwhelmingly of foreign fighters, it is deployed to assist in battles across the Islamic State. There is also an all-female Al-Khansaa Brigade tasked with policing religious laws. According to battle reports, ISIL often operates in small mobile fighting units.
The group also operates outside areas it largely controls using a clandestine cell system. An ISIL-linked senior militant commander in Sinai told Reuters; "They [ISIL] teach us how to carry out operations. We communicate through the internet, ... they teach us how to create secret cells, consisting of five people. Only one person has contact with other cells. They are teaching us how to attack security forces, the element of surprise. They told us to plant bombs then wait 12 hours so that the man planting the device has enough time to escape from the town he is in."
In sharp contrast to some other jihadist organizations such as the Caucasus Emirate which generally attempted to minimize their own casualties, ISIL is known for its willingness to sacrifice as many of its fighters as necessary to achieve its objectives. This is especially true in regard to ISIL's callous use of new recruits. When the militant organization still held large swaths in Syria and Iraq and had ample access to native as well as foreign volunteers, it usually barely trained new recruits. Instead of focusing on preparing for combat, training camps mostly indoctrinated new fighters into following orders and being willing for sacrifice one's life for ISIL. The organization's high command then used the inexperienced recruits for swarming and human wave tactics, often resulting in extremely high casualties. One high-ranking ISIL commander best known for this approach was Abu Omar al-Shishani who successfully employed swarming tactics during the Siege of Menagh Air Base and Battle of Al-Tabqa airbase. According to his reasoning, the enemy would eventually be overwhelmed or run out of ammunition regardless of the casualties among ISIL fighters. Regional expert Joanna Paraszuk sarcastically remarked that al-Shishani's tactics were based on the belief that "everyone want[s] to be a Shahid" (martyr). Though some ISIL frontline commanders did not espouse this readiness to sacrifice troops, the organization's high-command appears to care little about its common fighters.
Following the Siege of Kobanî which resulted in large losses among its veterans and commanders (including 2,000 militants killed), ISIL was forced to promote several inexperienced commanders and to rely even more than before on new recruits. As result, the tactics of ISIL's armed wing became even more crude and uncaring about its own forces. Paraszuk noted that the jihadists' strategies and tactics sometimes broke down completely due to this. For example, some troops were essentially ordered to "just run towards the [enemy] and fight or whatever" during the 2015 Battle of Hasakah, even though they were targeted by massive aerial bombardments and their attacks had no apparent strategic value.
Technicals play an important role for ISIL in a variety of combat purposes, ranging from quick-reaction forces to tank equivalents to self-defendable car bombs that can attack heavily defended targets.
In June 2014, ISIL had at least 4,000 fighters in Iraq. The CIA estimated in September 2014 that it had 20,000–31,500 fighters in Iraq and Syria. The Syrian Observatory for Human Rights estimates that the force numbers around 80,000–100,000 total (up to 50,000 in Syria and 30,000 in Iraq). Reuters quoted "jihadist ideologues" as claiming that ISIL has 40,000 fighters and 60,000 supporters, while an Iraqi Kurdish leader estimated in November 2014 that ISIL's military had 200,000 fighters. 85–600 Iraqi Kurds may have joined ISIL.
Some Syrian rebel factions have defected to ISIL, including the 1,000-strong Dawud Brigade in July 2014. In addition to jihadists and other volunteers, ISIL is known for forcing other rebel groups to fight for it, as well as conscripting individuals.
There are many foreign fighters in ISIL's ranks. In June 2014, The Economist reported that "ISIS may have up to 6,000 fighters in Iraq and 3,000–5,000 in Syria, including perhaps 3,000 foreigners; nearly a thousand are reported to hail from Chechnya and perhaps 500 or so more from France, Britain and elsewhere in Europe." Chechen leader Abu Omar al-Shishani, for example, was made commander of the northern sector of ISIL in Syria in 2013. According to The New York Times, in September 2014 there were more than 2,000 Europeans and 100 Americans among ISIL's foreign fighters. As of mid-September 2014, around 1,000 Turks had joined ISIL, and as of October 2014, 2,400–3,000 Tunisians had joined the group. An ISIL deserter alleged that foreign recruits were treated with less respect than Arabic-speaking Muslims by ISIL commanders and were placed in suicide units if they lacked otherwise useful skills. According to a UN report, an estimated 15,000 fighters from nearly 70 countries have travelled to Iraq and Syria to join militant groups, including ISIL.
Reuters has stated that according to jihadist ideologues, 10 percent of ISIL's fighters in Iraq and 30 percent of its fighters in Syria are from outside those countries.
As of September 29, 2015, the CIA estimated that 30,000 foreign fighters had come to join ISIL. As of October 2015, 21% came from Europe, 50% from Western Asia or North Africa, and 29% from elsewhere; according to the Global Terrorism Index and other sources, they were of the following nationalities:
List of nationalities of foreign fighters in ISIL
This is a list of nationalities of foreign fighters who joined ISIL from June 2014 to June 2018. This list does not include citizens of Syria, or Iraq. This list includes women and children who joined ISIL, some of whom may have been noncombatants. In total, 41,490 non-Iraqis and non-Syrians joined ISIL's main branch in these countries (32,089 were adult men), of whom 7,366 (5,930 were adult men) returned to their countries of departure, sometimes to face charges; most of the rest are presumed dead.
ISIL claimed their first ever attack in Kashmir Valley that left one police officer dead. Afterwards, a video surfaced of an ISIL soldier named Abu al-Baraa al-Kashmiri pledging allegiance to ISIL and forming the group Wilayat Kashmir. Abu al-Baraa is probably the leader of the group. In the video Abu al-Baraa called on Muslims in the Kashmir Valley to fight the Pakistani and the Indian governments and criticized the Islamic movement of Hizb-Lashkar-Jaish-Tehreek, declaring takfir and jihad on it. He called on members of other insurgent groups operating in Kashmir (such as Ansar Ghazwat-ul-Hind and its leader Zakir Musa) to pledge allegiance to ISIL, accusing the leaders of other insurgent groups of working for Pakistan's Inter-Services Intelligence.
ISIL shot down an Iraqi helicopter in October 2014, and claims to have shot down "several other" helicopters in 2014. Observers fear that they have "advanced surface-to-air missile systems" such as the Chinese-made FN-6, which are thought to have been provided to Syrian rebels by Qatar and/or Saudi Arabia, and purchased or captured by ISIL.
ISIL also captured many inoperable fighter aircraft after capturing the Syrian airbase of Al-Tabqa. The Syrian Observatory for Human Rights reported in October 2014 that former Iraqi pilots were training ISIL militants to fly captured Syrian jets. Witnesses reported that MiG-21 and MiG-23 jets were flying over al-Jarrah military airport, but the US Central Command said it was not aware of flights by ISIL-operated aircraft in Syria or elsewhere. On 21 October, the Syrian Air Force claimed that it had shot down two of these aircraft over al-Jarrah air base while they were landing.
ISIL has a long history of using truck and car bombs (SVBIEDs), suicide bombers, and IEDs. It has become especially adept at the construction and use of SVBIEDs, most notably quite sophisticated models which were fitted with armour, machine guns, and/or firing ports. These are mixtures of car bombs and technicals ("suicide bomber technical") that can approach heavily defended targets, suppressing the enemy while being protected from small-arms fire. Sometimes, ISIL even used armoured personnel carriers as chassis for car bombs, or fitted SVBIEDs with unguided rockets to clear the path to the intended target.
ISIL captured nuclear materials from Mosul University in July 2014. In a letter to UN Secretary-General Ban Ki-moon, Iraq's UN Ambassador Mohamed Ali Alhakim said that the materials had been kept at the university and "can be used in manufacturing weapons of mass destruction". Nuclear experts regarded the threat as insignificant. The International Atomic Energy Agency said that the seized materials were "low grade and would not present a significant safety, security or nuclear proliferation risk".
Reports suggested that ISIL captured Saddam-era chemical weapons from an Iraqi military base, and the group also enlisted the aid of scientists living in its territories to produce their own chemical weapons. ISIL managed to produce its own mustard gas, and employed it on battlefields in Iraq and Syria. According to one scientist involved in the project, the main value of the mustard gas to ISIL was not its impact on actual combat, but its effect in psychological warfare. The production of chemical weapons slowed greatly from early 2016, however, as the United States and the Iraqi government targeted production facilities and killed or captured the leaders of the programme. Regardless, it is generally believed that ISIL remains in possession of hidden data and equipment to restart the production of chemical weapons in the future.
ISIL deployed mustard gas and chlorine gas against forces of the Iraqi government, the Syrian government and the Syrian opposition, as well as unidentified chemical weapons against the Syrian Democratic Forces. According to the US military, ISIL used the chemical weapons effectively on a tactical level, but never managed to employ them in a way that impacted the larger strategic situation. The group produced not enough chemical weapons, being hampered not just by airstrikes and raids, but also lack of skilled personnel and equipment.