Iran and the Islamic State

Iran opposed the Islamic State as a threat to its interests, to the governments it supported in Baghdad and Damascus, and to Shiite communities and religious sites.[1][3] Its campaign involved direct military assistance, advisers, weapons, surveillance, support for militias, and missile strikes launched from Iranian territory.[4][7] The Islamic Revolutionary Guard Corps’ Quds Force, which conducts operations beyond Iran’s borders, organized and supported ground forces against the group, particularly Iran-backed Iraqi militias.[8][9]

The conflict connected several distinct security problems: the Islamic State’s territorial expansion near Iran, threats to Iran’s regional allies, and terrorist recruitment and attacks within Iran itself.[2][3][7] Iranian support for Syrian president Bashar al-Assad preceded the Islamic State’s emergence, beginning in 2012 and subsequently expanding as jihadist groups gained strength.[3] Fighting the Islamic State therefore formed part of a broader intervention rather than the sole explanation for Iran’s involvement in Syria.[3][4]

Iran and Iran-supported forces contributed to reversing the Islamic State’s territorial gains, alongside the U.S.-led coalition in Iraq and Russia in Syria.[1] These overlapping campaigns did not make Iran and the United States military partners: some operations took place separately, while Iran-aligned militias later attacked coalition forces and disrupted counter-Islamic State operations.[10][6] Iran’s opposition to the Islamic State and the conduct of its allied armed groups consequently require separate treatment.[1][6]

The Islamic State’s June 2014 offensive brought its forces to within 50 miles of Iran’s border.[7] By July, the organization controlled territory in northern and western Iraq and parts of eastern Syria. A Globes commentary described Iran, the United States, and Russia as helping the Iraqi government of Nouri al-Maliki mount a counterattack against its advance.[11] The organization’s claim to a Sunni caliphate was not recognized by Shiite Muslims.[11]

Iran responded by supplying the Baghdad government and the Kurdistan Regional Government’s peshmerga with Quds Force advisers, drone surveillance, weapons shipments, and other direct military assistance.[7] It also reportedly accepted the replacement of its longtime ally Maliki by Haider al-Abadi, who pledged fuller inclusion of Sunni leaders.[7] Military assistance thus accompanied an adjustment to the political leadership of the Iraqi government Iran supported.[7]

A 2014 analysis by the Jerusalem Center for Security and Foreign Affairs interpreted the Islamic State’s expansion as a threat to Iranian influence in Syria and Lebanon and to Shiite communities and holy places.[12] It reported that Revolutionary Guard, Basij, Hezbollah, and other Shiite fighters had died defending the tomb of Zainab in Syria.[12] The same analysis reported Iranian-media claims that approximately 5,000 volunteers had joined a group formed to defend Shiite holy places in Iraq, alongside a border police proposal to add 160 inspection points, particularly on the northwestern frontier.[12]

After the Iraqi army’s collapse in June 2014, Iran-backed Shiite militias became central participants in battles against the Islamic State.[8] During the siege of Amerli, fighters from three militias coordinated with the Iraqi army, one another, and Quds Force advisers; the forces that broke the siege also received U.S. air support.[8] Iran’s assistance to these groups included political backing, weapons, funding, advisers, training, and operational coordination.[8]

Iranian strikes in late November 2014 helped drive Islamic State fighters from Saadiya and Jalawla in Iraq’s Diyala province.[10] Iranian and U.S. operations there were separate and reportedly occurred without coordination between their leaders.[10] Iraqi operations to retake Tikrit began on March 2, 2015, after the Islamic State had held the city since June 2014.[13] Iran assisted the Iraqi military with drones, heavy weapons, and ground troops, while U.S. intelligence services confirmed Iranian supplies of missiles, rockets, and other munitions to Iraqi security forces.[13]

In Syria, Iran supported Assad’s government and later sent Revolutionary Guard units as jihadist organizations grew stronger.[3] Its assistance to the Iraqi government and Shiite militias likewise expanded as the Islamic State threat increased, encompassing equipment, training, and the building of volunteer militia forces.[3] The Quds Force shored up Assad’s government and helped Iraqi militiamen fight the Islamic State while strengthening Iran’s relationships with allied armed groups.[9]

In its account of the 2017 recapture of Mosul, the Jerusalem Center for Security and Foreign Affairs reported that Shiite militias, including the Popular Mobilization Forces, participated alongside Iraqi forces and that many received Iranian support.[14] It also reported Iranian officials’ praise for the militias and for Iran’s assistance.[14] In November 2017, Quds Force commander Qassem Soleimani was photographed in Abu Kamal after its capture, at a time when it was described as the Islamic State’s last stronghold in Syria.[15] A report that month placed Revolutionary Guard losses in Iraq and Syria at more than 1,000 personnel, including senior commanders; that figure covered the two theaters rather than only deaths in combat against the Islamic State.[15]

The Islamic State also developed a record of attacks within Iran.[2][16] On June 7, 2017, five attackers armed with rifles, grenades, and suicide vests struck parliament and the mausoleum of Ayatollah Ruhollah Khomeini in Tehran: three attacked parliament and two targeted the mausoleum.[2] At least 17 people were reported killed and more than 50 injured, and the organization claimed responsibility, released footage, and called for further attacks.[2] The attackers were reported to have fought for the Islamic State in Iraq and Syria before returning to Iran to prepare the operation.[2]

The organization’s claim was accompanied by a video statement declaring: “This is a message from the soldiers of Islamic State in Iran, soldiers of the first brigade of Islamic State in Iran which, God willing, won’t be the last.”[2] Iranian authorities identified the attackers as Iranian citizens who had joined the organization.[17] Afterward, Iranian officials said the regional campaign would continue, including the dispatch of fighters to Iraq and Syria alongside allied Shiite militias.[18]

In September 2018, the Islamic State claimed an attack on a military parade in Ahvaz that killed 25 people and injured 70.[16] On October 26, 2022, a gunman attacked the Shah Cheragh shrine in Shiraz, and the organization again claimed responsibility, presenting the attack in explicitly anti-Shiite terms.[16] The Washington Institute reported 15 people killed and at least 40 injured.[16] A further Islamic State attack in Iran followed in August 2023.[5]

On January 3, 2024, two explosions struck a gathering near the Martyrs Cemetery in Kerman during a ceremony marking the fourth anniversary of Soleimani’s death.[19] The Islamic State claimed responsibility, and the State Department identified the bombing as an Islamic State–Khorasan Province operation.[6][19] Reports placed the death toll between 84 and 95 and recorded approximately 284 injuries.[6][19]

The Kerman attack formed part of Islamic State–Khorasan Province’s expanding transnational operations.[5] Iranian and Turkish investigations linked the cells involved in the January 2024 Kerman and Istanbul attacks to the branch’s wider network, and the Kerman attackers had traveled to Turkey and Afghanistan.[5] Iranian authorities said they arrested 35 people in January in connection with the bombings, including an ISIS-K commander.[20]

The Quds Force’s organization of ground forces and its relationships with Iraqi militias were central instruments of Iran’s anti-Islamic State campaign.[8][9] Soleimani led the force from 1998, strengthened Iranian ties with Assad’s government and Iraqi Shiite militia groups, and played a prominent operational role in the fighting.[9] An Iraqi former senior official described him as a commander who visited the front to inspect troops and combat operations.[9]

Iran’s support combined assistance to recognized governments with support for armed groups operating alongside them.[4] Iraqi security forces, including Kurdish peshmerga, confronted the Islamic State alongside Iranian-backed Shiite militias, whose Iranian training and funding increased after the organization’s advance.[21] Training supplied by the Quds Force and Lebanese Hezbollah was used both against the Islamic State in Iraq and in support of Assad’s government in Syria.[21] These activities connected the anti-Islamic State campaign to the wider military infrastructure of Iran’s regional alliances.[4][21]

Iran also used ballistic missiles to strike targets it identified as Islamic State facilities.[4][22] On June 18, 2017, the Revolutionary Guard said it fired six Zolfaqar medium-range ballistic missiles from western Iran toward command, logistics, and vehicle-bomb targets in Syria’s Deir al-Zour province.[22] Iran presented the operation as retaliation for the Tehran attacks eleven days earlier.[22] The strike was not Iran’s first ballistic-missile use since 1988: the Washington Institute noted at least six reported Iranian Scud launches against Mujahedin-e Khalq bases in Iraq between 1994 and 2001. It instead described the 2017 operation as the first combat use of one of Iran’s newer indigenous missile designs.[22]

On October 1, 2018, Iran fired six ballistic missiles from western Iran at suspected Islamic State positions near Hanjin in Syria.[4] It said this strike retaliated for the attack on the Ahvaz military parade.[4] The operation also demonstrated the capacity to project military power into Syria directly from Iranian territory.[4]

Following the Kerman bombings in January 2024, Iran again launched missiles at Syrian sites that it said were used by the Islamic State.[23] Reporting identified targets in the Idlib area, including locations associated with other armed groups as well as areas said to be used for training Islamic State–Khorasan militants.[24] Iran also struck sites in Iraq that it alleged were used by Israeli intelligence; Iraq condemned those strikes as a violation of its sovereignty and recalled its ambassador from Iran.[23]

Domestic counterterrorism measures included arrests, weapons seizures, and announcements of disrupted cells.[16] Iranian authorities reported arresting ten suspects and seizing approximately 100 kilograms of explosives in 2016, and arresting eight suspects in Tehran in 2017.[16] Further arrests and weapons seizures followed the June 2017 attacks, and authorities announced the disruption of two cells in February 2019.[16] These episodes represent reported enforcement actions and official claims about plots, rather than completed Islamic State attacks.[16]

An Iranian official interviewed after the Tehran attacks said the Islamic State had developed a support network within Iran and identified political and economic grievances, as well as religious extremism, as possible recruitment factors.[18] Most Iranian Sunnis rejected the organization’s ideology.[18] In its analysis of the attacks, the Jerusalem Center for Security and Foreign Affairs reported increased Persian-language propaganda in the preceding months and appeals for Iran’s Sunni minority to revolt and form cells.[25]

A spyware campaign disclosed in 2018 targeted Iranian Kurds and Iranian Islamic State supporters using decoy applications themed around the organization and a Kurdish news agency.[26] The campaign had operated since 2016, with an estimated 240 victims, 97 percent of them Iranian citizens; actual application downloads might have been higher.[26] Its perpetrators were unidentified, although the technical assessment judged the campaign likely to be Iranian in origin and potentially directed by government entities.[26]

Iran’s posture toward possible cooperation with Washington varied across officials and circumstances.[12][27] The Jerusalem Center for Security and Foreign Affairs interpreted contrasting 2014 statements as evidence of internal differences: Ali Shamkhani rejected cooperation, while presidential aide Hamid Abutalebi suggested that diplomacy between the two countries could resolve the Iraqi crisis.[12] President Barack Obama wrote to Supreme Leader Ali Khamenei in 2014 about their mutual interest in defeating the Islamic State, and Secretary of State John Kerry said in 2016 that Iranian involvement in Iraq was helpful in certain respects.[27] These contacts and overlapping interests did not establish joint military operations.[12][10]

The reversal of Islamic State territorial gains involved Iranian intervention and Iran-supported forces as well as the U.S.-led coalition in Iraq and Russia in Syria.[1] Iran sought to prevent the organization’s return while using its intervention and the group’s defeats to improve its own strategic position.[4] Its campaign therefore had both an anti-Islamic State dimension and consequences for the regional influence of Tehran and its allies.[3][4]

The protection of Shiite communities and holy places was a recurring element of Iranian mobilization.[3][12] The Jerusalem Center for Security and Foreign Affairs interpreted Iran’s support for Assad as serving a wider strategic purpose, describing Syria as both a defense line against Israel and a barrier against Islamic State incursions threatening Shiite communities in Lebanon.[28] Its analysis also described Iran and Hezbollah as planning and conducting offensives in Syria and identified Syria and Iraq as major theaters of Iran’s campaign against the Islamic State.[28]

Iranian leaders linked intervention abroad to security at home.[25] The Jerusalem Center for Security and Foreign Affairs reported Khamenei’s argument that failing to fight the Islamic State where plots were being prepared could expose Iran to similar attacks domestically.[25] The June 2017 assaults nevertheless demonstrated that a regional campaign did not prevent the organization from developing an operational presence inside Iran.[2]

The later prominence of Islamic State–Khorasan Province extended the conflict beyond the original Iraqi and Syrian battlefields.[5] The branch emerged in 2015 as an official Islamic State affiliate in the Afghanistan-Pakistan region and subsequently developed wider external-operations capabilities.[5] Threats against Iran preceded the 2022 Shiraz attack, and the branch’s subsequent network connected movement through Afghanistan and Turkey with the Kerman bombing.[16][5] The attacks also reflected the Islamic State’s hostility toward Shiites, whom its adherents view as outside Islam.[16]

Iran’s conflict with the Islamic State remained distinct from its confrontation with the United States and Israel.[23][6] Iran-aligned militias in Iraq and Syria attacked coalition forces in ways that disrupted counter-Islamic State operations, even though Iran and its partners had themselves fought the organization.[6] The simultaneous existence of these conflicts does not establish Iranian support for the Islamic State.[1][6]

Disputes concern both the behavior of Iran-backed militias and the strategic purposes of Iran’s intervention.[8][29] Sunni residents and relatives accused militias of burning homes, obstructing returns, kidnapping civilians, and killing people suspected of sympathizing with the Islamic State; militia representatives disputed allegations that they targeted Sunni civilians.[8] U.S. reporting also accused Kata’ib Hezbollah and other groups of serious abuses against primarily Sunni civilians and warned that incorporating Kata’ib Hezbollah, a designated Foreign Terrorist Organization, into the Popular Mobilization Forces could undermine counterterrorism objectives.[21][30] One 2015 strategic interpretation distinguished Iran’s vigorous campaign in Iraq from a more selective posture in Syria, where the Islamic State also weakened other opponents of Assad.[29]

Iran’s claims about the effectiveness of its June 2017 missile strike were disputed.[22] Analysis of available footage concluded that four of the six missiles appeared not to reach their intended targets and that the visible impacts were near misses.[22] The same assessment noted Israeli-source reports of seven launches, with several missiles landing in the Iraqi desert and only one or two approaching their targets.[22] Iranian claims of successful retaliation therefore did not establish the extent of damage.[22]

Iranian accusations linking Israel or Saudi Arabia to Islamic State attacks were allegations, not established responsibility.[31][19] Following Kerman, Iranian leaders pointed to Israel, while U.S. officials said they did not believe Israel was involved and the State Department attributed the bombing to ISIS-K.[6][19] Separately, a reported 2014 statement by Islamic State spokesman Abu Muhammad al-Adnani that the organization had not attacked Iran since its establishment was the group’s own account of its conduct, not independent evidence of Iranian–Islamic State cooperation.[32] The Jerusalem Center for Security and Foreign Affairs likewise acknowledged that reports of possible Iranian assistance to Abu Musab al-Zarqawi were difficult to verify.[32]