Iran–Israel Conflict During the Syrian Civil War

Iran’s strategic alliance with Syria dated to the early 1980s, and Tehran decided in 2011–2012 to intervene in the Syrian civil war to preserve that relationship and retain Syria as a base of regional influence, particularly for supporting Hezbollah in Lebanon.[1] Iranian military operations supporting Assad from 2011 intensified longstanding tensions with Israel, eventually bringing Iranian personnel, Hezbollah fighters, and other Iran-backed militias into a theater adjoining Israel’s northern border.[7] These forces supplied the Syrian government with manpower, training, equipment, weapons, and funding.[7]

Syria served several Iranian strategic interests: it provided a route for supplying Hezbollah, remained Iran’s closest Arab-state ally, and offered a barrier against both a potentially hostile Sunni opposition government and Sunni extremist groups threatening Hezbollah from Syrian territory.[8] The Islamic Revolutionary Guard Corps’ Quds Force conducted Iranian operations supporting regional allies through arms shipments, advisers, training, and financial assistance.[8] Syria also formed part of Iran’s approach of confronting threats beyond its own borders, often termed “forward defense,” linking Iran to the Levant and Mediterranean and offering a potential additional front against Israel alongside Lebanon and Gaza.[9]

The importance attached to Syria was expressed in a 2012 statement attributed to Iranian cleric Hujjat al-Islam Mehdi Taeb: “If we lose Syria we will not be able to maintain Tehran,” followed by his description of Syria as Iran’s “35th province.”[1] Iran’s investment extended beyond preserving Assad: its Syrian foothold also supported the development of forces capable of challenging Israel.[1] Its objectives encompassed military entrenchment and longer-term political and economic influence, while Israeli concerns focused on advanced weapons in Syria and transfers of precision-guided weapons to Hezbollah.[9]

Iran’s military role expanded in stages rather than beginning as a single large deployment.[1] During the war’s first two years, Iranian military activity was relatively limited and included sending Hezbollah fighters as advisers.[1] Reinforcements supporting Assad in 2012 included Quds Force members, recruits from Afghanistan and Pakistan, Iraqi Shiite militia members, and Hezbollah fighters; these forces helped reverse the momentum of anti-Assad armed groups and enabled government forces to begin recovering territory.[9]

In summer 2014, advances by ISIS and increasing danger to Assad’s government prompted Iran to reinforce its presence with hundreds of Revolutionary Guards, increase the Hezbollah contingent to approximately 5,000, and support additional foreign Shiite volunteers and Iraqi militias.[1] After government forces reached a low point in summer 2015, Iran and Russia increased their involvement together, with Iran reinforcing ground forces and Russia providing air support.[1] Russia entered the conflict directly in September 2015 with air and ground assets, following a reported Moscow meeting at which Qassem Soleimani offered Iranian ground forces and allied Iraqi and Lebanese fighters to operate alongside Russian air power.[10]

Iran’s network included more than its own uniformed personnel.[1] The National Defense Forces provided an umbrella for local militias trained and directed by the Revolutionary Guards, while foreign formations included the Afghan Fatemiyoun, Pakistani Zainebiyoun, and Iraqi groups such as the Hezbollah Brigades, Harakat Hezbollah al-Nujaba, and Asa'ib Ahl al-Haq.[1] Iran also developed relationships with local organizations, including Quwat al-Ridha and the Baqir Brigade.[1] Iranian Revolutionary Guard personnel in Syria were estimated to have peaked at approximately 2,500 in 2016, before declining as fighting subsided.[1]

Israel’s initial policy was to remain outside Syria’s internal struggle while making exceptions for threats to its security and for discreet humanitarian assistance to Syrians.[10] Those exceptions included responding to fire or shelling into Israeli territory, preventing sophisticated weapons transfers to Hezbollah, and preventing weapons of mass destruction from falling into terrorist hands.[10] Israel began generally acknowledging military action against Iranian missile shipments to Hezbollah in May 2013, alongside action against other facilities, including Syrian chemical-weapons sites.[10] Its early air campaign primarily targeted Iranian weapons shipments intended for Hezbollah in Lebanon.[11]

A 2015 symposium in the Jewish Review of Books characterized this approach as non-intervention in the civil war rather than abstention from every military action inside Syria.[12] Its contributors described competing strategic preferences: standing aside while Assad and his opponents fought, or acting to weaken Assad and Iran’s regional position.[12] They also emphasized Israel’s humanitarian assistance and the distinction between deliberate cross-border attacks and projectiles that sometimes reached Israel as a consequence of nearby fighting.[12]

From 2014, Iran sought to establish an additional front against Israel along the Golan Heights using Hezbollah fighters and local militias in southern Syria.[1] Activities included attempts to place explosive devices near the border fence and construct a rocket array facing Israeli positions on the Golan.[1] Israeli operations, resistance from southern Syrian rebels, partial Russian restraint, and the later removal of Soleimani from the arena impeded that effort.[1]

Israel stepped up operations against Iranian assets in Syria in 2016 as part of its “campaign between the wars,” intended to damage precision-weapons supply networks and prevent a threatening Iranian presence on Israel’s borders without triggering open war.[10] From late 2016, Iran helped Syrian government forces recover territory while seeking a more permanent military presence; by 2017, it was widely observed to be developing entrenched positions capable of projecting power beyond Syria.[7] Israeli leaders expanded their stated red lines from weapons shipments to permanent Iranian bases, advanced-weapons manufacturing facilities, and new fronts for attacks against Israel.[7][11]

Amos Yadlin and Ari Heistein, writing in the Jewish Review of Books, identify the September 7, 2017 strike at Masyaf in northwestern Syria as the beginning of a new phase of the campaign, known by the Hebrew acronym mabam.[3] They characterize the target as an Iranian weapons facility, also described as a “scientific research center,” and interpret the strike as part of an effort to obstruct both Iranian entrenchment and military infrastructure strengthening Iran or Hezbollah near Israel.[3] Their analysis presents the campaign as an attempt to prevent strategic threats while keeping Israel largely outside the civil war itself.[3]

Outgoing Israeli military chief Gadi Eisenkot later said that the campaign intensified in January 2017.[13] He described attacks several times a week, generally without public announcements, consisting mostly of airstrikes but also ground-launched missiles and special-forces raids.[13] Eisenkot said the Israeli air force dropped 2,000 bombs in Syria during 2018 and deliberately emphasized infrastructure rather than Iranian personnel to reduce Tehran’s grounds for retaliation.[13]

On February 10, 2018, Israel said an Iranian drone crossed from Syria into Israeli airspace and was shot down; the Israeli military identified the intercepting aircraft as an Apache helicopter.[14][13] Israel then attacked the Tiyas, or T-4, air base in central Syria, which it assessed to be the drone’s launch site.[14] Syrian antiaircraft fire brought down an Israeli F-16 participating in the operation, and its two crew members ejected over northern Israel.[14] One crew member was seriously injured.[15]

Israel followed with a larger round of strikes against eight Syrian and four Iranian military targets, including Syrian air defenses.[14] The operation was described as Israel’s largest strike in Syria since the 1982 Lebanon war, and its targets included a base outside Damascus associated with regime-protection units.[16] Syria fired additional surface-to-air missiles during this second round.[16] Eisenkot later said that ten Iranians, including an IRGC Air Force colonel, were killed in the Israeli operation.[13]

The February incident exposed both the direct Iranian-Israeli dimension of the conflict and the danger Syrian air defenses posed to Israeli aircraft.[17] An early assessment identified two possible purposes for the drone flight—a covert intelligence-capability test or a deliberate provocation—but did not establish which explained the incident.[17] Iran’s foreign-ministry spokesman denied that an Iranian aircraft had entered Israel and described Iran’s presence in Syria as advisory and undertaken with Syrian government consent.[15]

On April 9, 2018, a strike hit the T-4 base near Palmyra, a site associated with coordinating Iranian-backed militias.[18] Reports attributed the operation to Israeli F-15 aircraft and put the deaths at four Iranian military advisers and 14 people overall.[18] This preceded a much larger exchange the following month, in which Iranian-linked rocket fire toward Israeli positions and extensive Israeli retaliation brought the confrontation into the open.[19]

In the early hours of May 10, 2018, the Israeli military said the Quds Force launched 20 Grad and Fajr-5 rockets from southern Syria at Israeli military positions on the Golan Heights.[19] Israel reported that Iron Dome intercepted four rockets and that the remainder fell in Syria, with none landing in Israel.[20] A preceding Israeli preventive strike had targeted rocket launchers after suspicious activity was detected.[20] Another account described two Iranian attempts on the night of May 9–10 to fire at Israel through proxy operatives.[21]

Israel responded with Operation House of Cards, an air operation reported to have lasted approximately an hour and a half and struck more than 50 Iranian targets using F-15 and F-16 aircraft.[20] Targets included a Quds Force headquarters and weapons depots at Damascus International Airport, where advanced weapons, missiles, and rockets were reportedly stored.[20] Israel also reported striking Quds Force intelligence and logistics facilities, military and logistics centers in Al-Kiswah, a military base north of Damascus, intelligence systems and outposts, and positions in the Golan buffer zone.[22]

Syrian air-defense systems fired at Israeli aircraft, and Israel attacked those systems in turn.[19] Israel said it destroyed five Syrian air-defense batteries of Russian origin, while Russian officials claimed that Syrian defenses intercepted more than half the Israeli missiles.[22] The Israeli military said its aircraft returned safely; Syrian state media acknowledged damage to military bases and reported three deaths and two wounded, while a conflict monitor reported at least 23 pro-government fighters killed.[19] Israeli Defense Minister Avigdor Lieberman characterized the operation as having struck “almost all” Iranian infrastructure in Syria.[22]

The May exchange marked an expansion from attacks on supply routes, weapons transfers, factories, and capability-building personnel to extensive direct strikes on Iranian forces and infrastructure.[21] The stated purpose was both to prevent advanced threats from developing and to impose costs intended to deter further Iranian military construction in Syria.[21] The scale of Israel’s response was described as larger than any Israeli operation in Syria since the 1973 Yom Kippur War.[22]

Iran and Syria nevertheless signed a military-cooperation agreement in August 2018 that reportedly provided for Iranian advisers to remain in Syria.[7] Iranian officials continued to characterize their military presence as being at the Syrian government’s invitation.[7] Meanwhile, Russia’s air-defense presence complicated Israeli operational planning, although Israel and Russia maintained communications intended to deconflict their activities.[7]

On September 17, 2018, Israel struck military targets near Lattakia, Homs, and Hamah.[14] A Syrian antiaircraft battery responding to the strikes mistakenly shot down a Russian military surveillance aircraft, killing 15 Russian personnel.[14] Russia blamed Israel for using the aircraft as cover, an accusation Israel denied; the incident produced a serious diplomatic crisis.[23] Moscow subsequently supplied Syria with S-300 air-defense systems.[23]

Yadlin and Heistein argue that the episode demonstrated three risks of the campaign: escalation on Israel’s northern front, damage to relations with Russia, and danger to Israeli aircraft.[3] They describe regular information exchanges and operational protocols as essential to preventing unintended Israeli-Russian clashes, while warning that Russian criticism and stronger Syrian air defenses could weaken those arrangements.[3] Israeli strikes reportedly declined after the Russian aircraft’s loss.[24]

In January 2019, Prime Minister Benjamin Netanyahu said Israel had struck Iranian and Hezbollah targets in Syria “hundreds of times.”[7] On January 20, a missile launched from Syria toward the Golan Heights after an Israeli strike near Damascus airport was intercepted by Iron Dome.[25] Israel subsequently attacked Iranian and Syrian military targets, including Quds Force positions and air-defense batteries.[25] A more detailed account identified a large weapons store at Damascus airport, a training base, and an intelligence site among the targets, and reported that some Iranian personnel had evacuated installations before the strikes.[26]

Further exchanges continued during 2019.[7] Israel said it thwarted a planned explosive-drone attack near Damascus in August.[25] In November, four rockets were fired from Syria toward the Golan Heights and northern Galilee, followed by Israeli strikes on Iranian facilities and Syrian air defenses.[27] An Israeli official estimated that the retaliatory strikes killed between ten and 20 fighters, most of them Iranians.[27]

Iran and Syria signed another agreement on July 8, 2020, expanding military cooperation.[25] Estimates circulated of at least 125 Revolutionary Guard and pro-Iranian militia outposts across ten Syrian governorates in August 2020.[25] A June 2021 estimate placed Iranian and Iran-aligned military sites at approximately 131, stretching from Daraa and Damascus to Aleppo, Idlib, and Deir ez-Zur, alongside 116 Hezbollah strongholds, many near the Lebanese and Israeli borders.[1] In September 2021, Israel’s military intelligence chief described a sustained decline in Iranian personnel, although Iran was still believed to have as many as 3,000 military personnel in Syria.[25]

A public-information tally identified 145 aerial attacks attributed to Israel during 2018–2022, with approximately 18–22 annually in 2018 and 2019 and 32–36 annually in 2020, 2021, and 2022.[2] Targets included weapons stores, production facilities, military sites, and Syrian-regime-linked installations; approximately half the aerial attacks recorded in 2022 targeted sites linked to the Syrian government.[2] A separate estimate reported in March 2022 put the cumulative campaign since 2017 at at least 1,200 targets struck using approximately 5,500 munitions.[11]

Weapons routes remained central to the confrontation.[28] Shipments to Hezbollah moved by air, sea, and land, including through Latakia and along the route from Iraq’s Al-Qa’im crossing to Al-Bukamal in eastern Syria.[28] Infrastructure associated with Soleimani around the Imam Ali base at Al-Bukamal housed forces and weapons, including underground facilities.[28] Iranian commander Razi Mousavi was described as leading a supply operation involving shipments through Latakia.[28]

Israeli airstrikes in Syria continued during the wars against Hamas and Hezbollah after October 7, 2023.[29] On April 1, 2024, a strike in Damascus killed IRGC commanders and other personnel, including Brigadier General Mohammad Reza Zahedi, who led Iranian operations in Syria and Lebanon.[30] Iran described the destroyed building as diplomatic premises, while an Israeli military spokesperson declined to comment on responsibility and characterized it as a Quds Force military building disguised as a civilian facility.[30]

Iranian leaders vowed retaliation, and on April 13 Iran launched an aerial attack against Israel from Iranian territory, describing it as a response to the Damascus strike.[4] This was Iran’s first direct military action against Israel from its own territory and connected the Syrian confrontation to a direct interstate exchange.[4] Israeli operations in Syria continued afterward, including a special-forces raid against Syrian missile factories in September 2024.[29]

Assad’s government fell on December 8, 2024.[5] CRS assessed that the loss of Iran’s principal Syrian state ally greatly reduced Tehran’s ability to use Syria as a transport hub and host for weapons and forces.[6] Hezbollah, which had been an important component of Assad’s military effort, had been weakened by Israeli bombardment in Lebanon, and its fighters withdrew from Syria in October 2024.[31] Israeli Defense Minister Israel Katz called Assad’s fall a “severe blow” to Iran’s regional axis.[32] Iranian officials said that no Iranian forces remained in Syria after Assad’s overthrow.[6]

Before that transformation, the Israeli campaign had constrained but had not eliminated Iran’s military presence or Hezbollah’s weapons supply networks.[9][2] Weapons transfers and arms production continued, with strikes sometimes forcing Iran to adopt alternative routes rather than stopping the movement or manufacture of weapons altogether.[2] Iranian and Syrian adaptations included stronger defenses against air attack and underground weapons-production facilities.[2] A 2022 assessment described partial results: some forces were pushed away from the Syrian Golan, entrenchment efforts were damaged, weapons flows were reduced, and Iran and Hezbollah changed methods, but the campaign did not fundamentally eliminate the Iranian presence.[33]

The campaign also carried human costs beyond military installations and personnel.[5] During 2024, the Syrian Network for Human Rights attributed 26 civilian deaths, including four children and eight women, to Israeli attacks through November 1.[5] A March 26 airstrike attributed to Israel killed a United Nations aid worker in Deir Ezzor when a missile hit a building allegedly occupied by the IRGC beside his home.[5] These casualty accounts were reported through human-rights monitoring and investigative reporting rather than a comprehensive independently established total for the entire confrontation.[5]

Iran’s nonmilitary presence presented a different challenge from weapons stores or air bases.[9] Its activities included support for local communities, cultural and religious institutions, and educational programs, alongside political and economic relationships.[9] These efforts had limits, including reported antipathy toward Iran among many Syrians.[9] Nevertheless, the air campaign did not directly address Iran’s deeper economic, educational, cultural, and social influence.[2]

The confrontation evolved from largely secret and indirect hostility into a sustained campaign containing direct Iranian-Israeli exchanges.[26] By 2019 it was characterized as a low-level conflict carrying a risk of escalation into open warfare, particularly around the Golan Heights.[9] The February and May 2018 incidents demonstrated that an ostensibly limited campaign could involve Iranian aircraft, rocket attacks, extensive Israeli retaliation, and losses caused by Syrian air defenses.[14][22] The April 2024 sequence subsequently linked a strike in Syria to Iran’s first direct attack from Iranian territory.[4]

The “campaign between the wars” was a strategy rather than a single operation: kinetic, cyber, and cognitive actions sought to contain adversaries below the threshold of war and postpone a larger conflict.[2] In Syria, this became a broad kinetic effort principally aimed at restricting Iranian entrenchment.[2] Its targets extended beyond Iranian personnel to Hezbollah weapons transfers, militia facilities, production infrastructure, and Syrian military sites associated with cooperation with Iran.[2] The distribution of targets included 54 percent directed at Iranian targets, Hezbollah, or weapons transfers and 30 percent at pro-Iranian militias.[2]

Israeli officials argued that the campaign prevented a substantially larger Iranian force from taking shape.[9] Eisenkot described an Iranian vision associated with Soleimani of approximately 100,000 ground troops, supported by ground, aerial, naval, and intelligence capabilities; he said an existing force already included around 20,000 Hezbollah and other Shiite militia fighters and thousands of Iranian advisers.[34] Israel’s operational response emphasized destroying weapons-manufacturing facilities, keeping pro-Iranian forces away from the border, and limiting militia numbers.[34] These figures described the Israeli military leadership’s assessment of Iranian plans rather than an established deployment total.[34]

Yadlin and Heistein argue that removing every Iranian soldier from Syria was not an economically achievable Israeli objective and that priority should instead fall on advanced weapons and threatening infrastructure near Israel’s border.[3] They interpret a reported January 2019 strike at Quneitra, which they say killed Iranian and Hezbollah operatives, as evidence that Russian pledges to keep hostile forces away from the border had not been fulfilled.[3] Their analysis thus distinguishes the maximal goal of Iranian withdrawal from the narrower goal of denying specific capabilities.[3]

Assessments of deterrence likewise distinguish between preventing particular attacks and ending Iranian activity altogether.[2] Iran continued building capabilities even when Israeli strikes imposed operational costs, while Iranian-backed militias also attacked United States forces in Syria.[2] Five attacks on American bases and coalition troops in 2022 were attributed to Iranian militias, apparently in retaliation for Israeli airstrikes, illustrating that restraint toward Israel did not necessarily extend to other targets.[2]

The military purpose of particular operations and facilities was disputed, most notably the February 2018 drone’s mission and the status of the Damascus building struck in April 2024.[17][30] Accounts variously presented the drone as an intelligence platform or an intended attack vehicle, while Iran denied the Israeli account of its entry.[25][15] Iran characterized the Damascus target as diplomatic premises; Israel’s military spokesperson characterized it as a military facility.[30]

Reported force levels and attack totals use different dates, definitions, and geographic scopes.[9][25] An assessment of conditions as of August 1, 2019 estimated Iranian personnel in the high hundreds to low thousands at nearly 40 locations, alongside 10,000–20,000 Hezbollah and other Shiite militia fighters.[9] Later counts of outposts or strongholds therefore do not represent directly comparable measures of Iranian troop strength.[1][9] Public attack tallies also differ from counts of individual targets or munitions, and one reported total of more than 400 acknowledged strikes covered Syria and other Middle Eastern locations rather than Syria alone.[25]

Accounts of the May 2018 exchange differ on rocket numbers, interceptions, targets struck, and casualties.[13][26] Israeli accounts commonly reported approximately 20 rockets and four interceptions, while a competing account claimed closer to 50 rockets and no interceptions; other retrospective accounts gave 30 rockets, or described plans for approximately 60 launches.[35][26] Claims that Israel destroyed nearly all Iranian infrastructure represent Israeli officials’ characterizations, not an independently established inventory of destruction.[22] The 145-attack tally for 2018–2022 was expressly based on public information and carried a warning that it could contain inaccuracies.[2]