The Quds Force is one of five branches of Iran's Islamic Revolutionary Guard Corps (IRGC) specializing in unconventional warfare and military intelligence operations. U.S. Army's Iraq War General Stanley McChrystal describes the Quds Force as an organization analogous to a combination of the CIA and the Joint Special Operations Command (JSOC) in the United States. Responsible for extraterritorial operations, the Quds Force supports non-state actors in many countries, including Hezbollah, Hamas, Palestinian Islamic Jihad, Yemeni Houthis, and Shia militias in Iraq, Syria, and Afghanistan. According to Michael Wigginton et al., the Al-Quds Force is "a classic example of state-sponsored terrorism."
Since the Iranian Revolution in 1979, the Islamic Republic of Iran has been embroiled in tense relations with the U.S. and its allies. Following the overthrow of the American-backed Shah and a hostage crisis, both countries severed relations. Since then, both countries have been involved in numerous direct confrontations, diplomatic incidents, and proxy wars throughout the Middle East, which has caused the tense nature of the relationship between the two to be called an 'international crisis'. Both countries have often accused each other of breaking international law on several occasions. The U.S. has often accused Iran of sponsoring terrorism and of illegally maintaining a nuclear program, as well as using strong rhetoric against Israel, of which Iran has questioned its legitimacy and its right to exist while supporting Hamas, an antizionist group in the Gaza Strip. Meanwhile, Iran has often accused the U.S. of human rights violations and of meddling in their affairs, especially within the Iranian Democracy Movement.
Qasem Soleimani was an Iranian military officer who served in the Islamic Revolutionary Guard Corps (IRGC). From 1998 until his assassination by the United States in 2020, he was the commander of the Quds Force, an IRGC division primarily responsible for extraterritorial and clandestine military operations, and played a key role in the Syrian Civil War through securing Russian intervention. He was described as "the single most powerful operative in the Middle East" and a "genius of asymmetric warfare," and former Mossad director Yossi Cohen said Soleimani's strategies had "personally tightened a noose around Israel's neck." In his later years, he was considered by some analysts to be the right-hand man of the Supreme Leader of Iran, Ali Khamenei, and the second-most powerful person in Iran behind Khamenei.
Kata'ib Hezbollah or the Hezbollah Brigades, is a radical Iraqi Shiite paramilitary group which used to be part of the Iraqi Popular Mobilization Forces (PMF), staffing the 45th, 46th, and 47th Brigades. During the Iraq War (2003–11), the group fought against Coalition forces. It has been active in the War in Iraq (2013–2017) and the Syrian civil war (2011–present). The group was commanded by Abu Mahdi al-Muhandis until he was killed in a US drone attack in 2020. Thereafter, he was replaced by Abdul Aziz al-Muhammadawi, as the new leader of the PMF. KH seeks to establish an Iran-aligned government in Iraq, expel American forces from the country, and advance the regional and international interests of Iran in Iraq and the region. The group is responsible for killing hundreds of U.S. soldiers and takes a central part in carrying out attacks against U.S. targets in Iraq and acts as part of the Axis of Resistance. Kata'ib Hezbollah has received extensive training, funding, logistic support, weapons, and intelligence from the Quds Force of Iran's Islamic Revolutionary Guard Corps (IRGC).
The Islamic Republic of Iran and the Syrian Arab Republic are close strategic allies, and Iran has provided significant support for the Syrian government in the Syrian civil war, including logistical, technical and financial support, as well as training and some combat troops. Iran sees the survival of the Syrian government as being crucial to its regional interests. When the uprising developed into the Syrian Civil War, there were increasing reports of Iranian military support, and of Iranian training of the National Defence Forces both in Syria and Iran. From late 2011 and early 2012, Iran's IRGC began sending tens of thousands of volunteers in co-ordination with the Syrian government to prevent the collapse of the Syrian Arab Army; thereby polarising the conflict along sectarian lines.
The Iranian intervention in Iraq has its roots in the post-2003 invasion of Iraq by the United States and allies when the infrastructure of the Iraqi armed forces, as well as intelligence, were disbanded in a process called "de-Ba'athification" which allowed militias with close ties to Tehran to join the newly reconstituted army.
On 18 June 2017, under Operation Laylat al-Qadr, Iran's Islamic Revolutionary Guard Corps (IRGC) fired six surface-to-surface mid-range ballistic missile from domestic bases targeting ISIL forces in the Syrian Deir ez-Zor Governorate in response to the terrorist attacks in Tehran earlier that month. Next day, the IRGC published aerial videos recorded by the Damascus-based IRGC drones flying over the city during the operation, confirming that the missiles had successfully hit the targets with precision.
The May 2018 Israel–Iran clashes were a series of short military confrontations between Israeli and Iranian forces in Syria. On 10 May 2018 the Israeli military stated that Iranian forces in Syria launched 20 rockets against Israeli army positions on Western Golan Heights. The Syrian Observatory for Human Rights said that the attack occurred after Baath, a town in the demilitarised zone, was bombarded by Israeli forces. According to the Israel Defense Forces (IDF) some missiles were intercepted by Israel's Iron Dome system, while some fell short in Syrian territory.
On 1 October 2018, under the code name Operation Strike of Muharram, Iran's Islamic Revolutionary Guard Corps (IRGC) conducted missile and drone strikes against the Islamic State of Iraq and the Levant based east of the Euphrates river in Syria in retaliation to the Ahvaz military parade attack the previous week.
The Iran–Israel conflict during the Syrian civil war refers to the Iranian–Israeli standoff in and around Syria during the Syrian conflict. With increasing Iranian involvement in Syria from 2011 onwards, the conflict shifted from a proxy war into a direct confrontation by early 2018.
The 2019 Israeli airstrikes in Iraq began as unidentified drone or aircraft bombings of the Iranian-backed Popular Mobilization Forces (PMF) bases in Iraq starting on 19 July 2019. The strikes targeted Iranian proxy groups, based in Iraq, as well as IRGC operatives.
The US intervention in the Syrian civil war is the United States-led support of Syrian opposition and the Federation of Northern Syria during the course of the Syrian Civil War and active military involvement led by the United States and its allies — the militaries of the United Kingdom, France, Jordan, Turkey, Canada, Australia and more — against the Islamic State of Iraq and the Levant (ISIL) and al-Nusra Front since 2014. Since early 2017, the U.S. and other Coalition partners have also targeted the Syrian government and its allies via airstrikes and aircraft shoot-downs.
On 29 December 2019, the United States conducted airstrikes against Kata'ib Hezbollah's weapons depots and command centers in Iraq and Syria, reportedly killing at least 25 militiamen and wounding 55 more. The U.S. Department of Defense said the operation was in retaliation for repeated attacks on Iraqi military bases hosting Operation Inherent Resolve (OIR) coalition forces, particularly the 27 December 2019 attack on a Kirkuk airbase that left an American civilian contractor dead. Kata'ib Hezbollah, an extremist Shi'ite militia funded by Iran, denied any responsibility for the attacks.
A series of airstrikes were carried out by the Israeli Air Force on multiple Iranian-linked targets in the Deir ez-Zor Governorate of Syria on 13 January 2021. 57 people were killed according to Israeli reports. Iranian sources confirmed the strikes, but said that only Syrian Army positions were hit. Israel carried out another airstrike in Hama nine days later, killing a family of four, including two children, according to Syrian state media.
On 28 June 2021, President Biden directed airstrikes against Iran-backed militia groups close to the Syria-Iraq border. F-15E and F-16 aircraft were used to launch the attack in what the U.S. described as a retaliatory attack against U.S. facilities and personnel in Iraq by militia groups. Two operational and weapons storage facilities were targeted in Syria, the U.S. military revealed in a statement. Despite the U.S. not disclosing the information regarding the casualties in the attack, the SOHR stated that at least nine Iran-backed Iraqi militia fighters died, leaving many others injured. Iraqi militia groups aligned with Iran in a statement named four members of the Kataib Sayyed al-Shuhada faction they said were killed in the attack on the Syria-Iraq border.
The following is a timeline of the Syrian civil war for 2021. Information about aggregated casualty counts is found at Casualties of the Syrian civil war.
On March 23, 2023, at 1:38 p.m. local time (UTC+03:00), a kamikaze drone allegedly of Iranian origin struck a coalition base at Abu Hajar Airport near Rmelan, al-Hasakah Governorate in northeastern Syria. As a response, The US military carried out a series of attacks using F-15 Fighters at the direction of President Joe Biden. On 24 March 2023, two retaliatory strikes at near oil and gas fields known as Conoco in the vicinity of Deir Ezzor by multiple rockets and at Green Village by three drones targeted US and coalition forces.
Starting on 17 October 2023, and in response to United States support for Israel in the Israel–Hamas war, Iran-backed militias initiated a coordinated series of more than 170 attacks on U.S. military bases and assets in Syria, Iraq, and Jordan. These attacks resulted in injuries to dozens of U.S. service members. In retaliation, the U.S. has launched multiple counterattacks, resulting in the death of over 30 militants including a senior commander of the Nujaba Movement, Mushtaq Talib al-Saidi.
On 28 January 2024, an attack drone, launched by the Islamic Resistance in Iraq—an Iranian-backed Shia militia group—struck Tower 22, a U.S. military outpost in Rukban, northeast Jordan. The explosion resulted in the deaths of three U.S. soldiers and injuries to 47 others.
On 2 February 2024, the United States Air Force launched a series of airstrikes targeting Iran's Revolutionary Guards and Iran-backed militia groups located in Iraq and Syria. The attack was launched in retaliation against a drone strike carried out by the Islamic Resistance in Iraq targeting US troops in Jordan the week before, which killed three U.S. troops.
United States 
Iranian-backed militias (alleged)