Syria and Iran are strategic allies. Syria is usually called Iran's "closest ally", with ideological conflict between the Arab nationalism ideology of Syria's secular ruling Ba'ath Party and the Islamic Republic of Iran's pan-Islamist policy notwithstanding. Iran and Syria have had a strategic alliance ever since the Iran–Iraq War, when Syria sided with non-Arab Iran against its fellow Baath-ruled neighbor but enemy Iraq and was isolated by some Arab countries. The two countries shared a common animosity towards the late Iraqi president Saddam Hussein and coordination against the United States and Israel. Syria cooperates with Iran in smuggling arms to Hezbollah in Lebanon, since Israel has attacked Syria. During the Syrian Civil war Iran has conducted "an extensive, expensive, and integrated effort to keep Syrian President Bashar al-Assad in power."
Iran–Syria relations changed dramatically after the Iranian Revolution of 1979. Syria's strategic alliance with Egypt ended around the same time due to Egypt's treaty with Israel. Post-Revolution Iran represented an opportunity for Syrian President Hafez al-Assad to find a new counterweight to Israel and Iraq, Syria's regional foes. Meanwhile, new Iranian leader Ayatollah Khomeini saw Syria as a conduit to the Shia community in Lebanon. Mostafa Chamran, a close adviser to Khomeini, had experience fighting in Lebanon and advocated an Iranian alliance with Assad to increase their influence in southern Lebanon.
The relationship between Iranian and Syrian governments has sometimes been described as the Axis of Resistance. Syria was the first Arab state and the third in general, after the Soviet Union and Pakistan, to recognize the Islamic Republic that was founded in February 1979. Specifically Syria officially recognized the Islamic Republic on 12 February 1979. However, Assad did not visit Iran while Khomenei was alive, as the Ayatollah did not consider Assad to be a true Muslim. The Syrian leadership, including the current President Bashar Assad himself, belongs predominantly to the Alawite branch of Shi'a Islam. However, the relations between two countries do not depend on religious causes, because Syria is a secular state, while Iran is an Islamic republic. Instead, their ties are driven by common political and strategic points.
One of the first major fronts of the Iran–Syria alliance was Iraq. During the Iran–Iraq War, Syria sided with non-Arab Iran against Iraq and was isolated by Saudi Arabia and some of the Arab countries, with the exceptions of Libya, Lebanon, Algeria, Sudan and Oman. As one of Iran's few Arab allies during the war, Syria shut down Iraqi oil pipeline of Kirkuk–Baniyas pipeline to deprive the Iraqis of revenue. Syria also trained Iranians in missile technology and provided Iran with Scud B missiles between 1986 and 1988. In return for Syria's war support, Iran provided Syria with millions of free and discounted barrels of oil throughout the 1980s. In addition, Khomeini was restrained in his condemnation of the 1982 Hama massacre.
The second major area of cooperation between the two countries was in Lebanon during the Lebanese Civil War. Iran's Islamic Revolutionary Guards Corps, with Syrian assistance, established and trained the Hezbollah group to spread Khomeini's ideology and repel the 1982 Israeli invasion of southern Lebanon. Iran and Syria viewed Hezbollah as a useful lever against Israel and a way to establish greater influence in Lebanese affairs.
Iran and Syria had occasional differences in policy. In the mid-to-late 1980s, Syria maintained support for the non-Islamist Shia Amal Movement in Lebanon, even as Iran tried to maximize Hezbollah's power among Lebanese Shia. Although Iran was deeply ambivalent about the American-led intervention to remove Saddam Hussein from Kuwait, Syria participated in the coalition of nations to fight Iraq. Still, these disagreements never threatened to derail the relationship.
The alliance deepened in 2000 when Hafez's son Bashar al-Assad took over as President of Syria. Subsequent events like the Iraq War, the "Cedar Revolution", and the 2006 Lebanon War brought the countries closer together. Syria became increasingly dependent on Iran for political and military support as Assad was unable to maintain positive ties with other Arab powers during this time.
On 16 June 2006 the defense ministers of Iran and Syria signed an agreement for military cooperation against what they called the "common threats" presented by Israel and the United States. Details of the agreement were not specified, however then Syrian defense minister Najjar said "Iran considers Syria's security its own security, and we consider our defense capabilities to be those of Syria." The visit also resulted in the sale of Iranian military hardware to Syria. In addition to receiving military hardware, Iran has consistently invested billions of dollars into the Syrian economy.
Currently, Iran is involved in implementing several industrial projects in Syria, including cement factories, car assembly lines, power plants, and silo construction. Iran also plans to set up a joint Iranian–Syrian bank in the future. On 17 February 2007, Presidents Ahmadinejad and Assad met in Tehran. Ahmadinejad afterwards declared that they would form an alliance to combat U.S. and Israeli conspiracies against the Islamic world.
Syrian civil war
During the Syrian Civil War since 2011, Iran has aided the Syrian government. The Guardian has claimed that in May the Iranian Revolutionary Guard increased its "level of technical support and personnel support" to strengthen Syria's "ability to deal with protesters," according to one diplomat in Damascus. Iranian Sr. Foreign Policy Advisor Ali Akbar Velayati declared, "Iran is not prepared to lose this golden counterweight [to Israel]."
Iran reportedly assisted the Syrian government sending it riot control equipment, intelligence monitoring techniques and oil. It also agreed to fund a large military base at Latakia airport. The Daily Telegraph claimed in August 2011 that a former member of Syria's secret police reported "Iranian snipers" had been deployed in Syria to assist in the crackdown on protests. According to the U.S. government, Mohsen Chizari, the Quds Force's third-in-command, visited Syria to train security services to fight against the protestors.
In late June 2011, the Supreme Leader Ali Khamenei, stated in regards to the uprising: "In Syria, the hand of America and Israel is evident;" and in regards to the Syrian government: "Wherever a movement is Islamic, populist, and anti-American, we support it." Other Iranian officials have made similar pronouncements identifying the U.S. government as the origin of the uprising. However, in late August, the Iranian government gave its "first public sign" of concern over Syrian's handling of its crisis when foreign minister Ali Akbar Salehi issued a statement including the Syrian government in the list of states he urged to "answer to the demands of its people."
Syrian dissident and academic Murhaf Jouejati argues that Iran's contingency plan for its interests in Syria, in case the current pro-Iran government is overthrown, is to ethnically fragment the country in such a way that Iran could support an independent Alawite state.
Iran opened its first cultural center in Syria in 1983, located in the Mazzeh neighborhood of Damascus. It was later moved into the heart of Damascus next to Martyrs Square. The goals of the center include increasing cultural, scientific, and religious exchanges between the two countries, as well as being a forum for Iranian Islamic culture and Farsi. The cultural center cooperates with four Syrian universities to encourage the teaching of Farsi.
While Iran has showed an interest in spreading its culture to Syria, Syria has not been as motivated to spreading its culture to Iran. It is already common for Iranians to study Arabic, and Assad's regime did not want to spread any revolutionary messages. It was only in 2005 that Syria opened its first cultural center in Iran, which has become popular with Iranians seeking to learn Arabic. 
The largest cultural ties between Iran and Syria come from religious tourism. In 2008, 333,000 Iranians visited Syria as tourists, most of whom came to make religious pilgrimages to shrines like Sayida Zaynab. Iran has helped in the renovation and expansion of Shia shrines in the country in Damascus and Raqqa. According to Nadia von Maltzahn, the author of a book on cultural diplomacy between Syria and Iran, the large amount of religious tourism from Iran has given Syrians the idea that all Iranians are "religious, of modest background, and conservative, which did not persuade many Syrians to visit Iran." 
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|Wikimedia Commons has media related to Iran–Syria relations.|
- The Iran-Syria Nexus and its Implications for the Region: Hearing before the Subcommittee on the Middle East and North Africa of the Committee on Foreign Affairs, House of Representatives, One Hundred Thirteenth Congress, First Session, July 31, 2013