
A coup d'état took place in Syria in February of 1966, one supported by the Soviet Union. This was followed by another coup d’état four years later in 1970, called the Corrective Movement. This one put Hafez Assad in power in Syria on November 13, 1970. In 1971, under an agreement with President Hafez al-Assad, the Soviet Union was allowed to open its naval military base in Tartus. The base gave the Soviet Union a significant presence in the Middle East. During al-Assad's presidency from 1971 to 2000, thousands of Syrian military officers and educated professionals studied in Russia. The Soviets supported Syria during the Yom Kippur War, when thousands of Soviet advisors and technicians aided the Syrian army. The Soviets supplied over 3750 tons of aid to Syria during the war to Syria, and another 63,000 tons after the war at the end of October 1973.
Relations between the two nations became strained in 1976. The Soviets were unhappy about Assad's military involvement in Lebanon. The Soviets feared a conflict between the Palestinian Liberation Organization (PLO) and the Assad regime, both of whom had Soviet support. Soviet leader Leonid Brezhnev demanded that the Syrians accede to his call for a retreat and the Soviets had frozen weapons supplies to Syria. In turn, Syria denied the Soviets access to its naval bases. The conflict was resolved as Syria was hurt economically and approached the Soviets, hat in hand. In April 1977, Hafez al-Assad visited Moscow and met with Soviet leaders Leonid Brezhnev and Alexei Kosygin to bring about improved Syrian relations with the USSR. Unlike other Arab nations, Assad refused to condemn the 1980 Soviet invasion of Afghanistan. In October 1980, Syria and the Soviet Union signed a twenty-year Treaty of Friendship and Cooperation. Soviet military personnel remained in Syria, and the bulk of Syrian weapons came from the USSR and its allies.
Hafez al-Assad died on 10 June 2000 and was succeeded on 10 July 2000 by his son Bashar al-Assad. A period of civil unrest began in Syria in the early spring of 2011, part of the Arab Spring protests. Nationwide protests against President Bashar al-Assad's government began and the Syrian President responded by ordering violent crackdowns on the protesters. Militant opposition movements and massive defections from the Syrian Army followed, transforming the conflict from a civil uprising to an armed rebellion, and later a civil war. The rebel Free Syrian Army was created on July 29, 2011, with many other factions being created either out of the Free Syrian Army or independently. By 2012 the U.S was running covert operations in aid of militant groups fighting the Assad government. On March 6, 2013, the Arab League gave its member nations permission to arm the Syrian rebels and later that month the Arab league recognized the National Coalition for Syrian Revolutionary and Opposition Forces, as the legitimate representatives of the Syrian people.
By 2014, the Islamic State (ISIL) claimed a significant part of Syria's territory. ISIL had been recognized as as a terrorist organization by a number of Western countries, including the U.S., Britain and France, and these nations began to participate in direct military action against ISIL on Syrian territory.
Russian economic interests in Syria, including arms sales, caused the Russian government to support the Syrian government. Many Syrian arms purchases are financed by Russian loans. Russian soldiers have fought and died during the war in support of the Syrian government. Russian officials estimate that as of January 2019, 112 soldiers have been killed since troops were sent to fight in Syria in 2015.
Both the US and other Western governments have called on Russia to change its position, unsuccessfully.
On July 19, 2011, Russian Prime minister, Dmitri Medvedev said he was working with German Chancellor Angela Merkel to find consensus for a strategy to persuade the Syrian government to begin a constructive dialogue with protesters. Russia did not oppose a UN resolution condemning the violence in Syria, saying it would not do so as long as the resolution did not include sanctions or other "pressures". But on August 23, the Russian delegation to the UN, along with those of China and Cuba, denounced a UN inquiry into human rights violations by the Assad government. On October 4, Russia and China exercised their veto against a Western-drafted Security Council resolution. The resolution called for an end to all violence in Syria, and for accountability for those responsible for it and said the Security Council would review Syria's compliance with the resolution in 30 days after which the Council would "consider options."
On February 7, 2012, Russian Foreign Minister Sergei Lavrov, along with foreign intelligence chief Mikhail Fradkov, met with President Assad and reported to the world that President Assad was committed to reform of the constitution and electoral process. But a month later, in March, Lavrov said in a televised interview that Syria's leadership had ignored Russia's warnings and made "very many mistakes" that helped drag the country to the brink of civil war.
There was much back and forth in the United Nations and the Russians attempted to appear to play the role of peacemaker. Following the Houla massacre in May of 2012, Foreign Minister Sergey Lavrov said that "The government bears the main responsibility for what is going on" adding that "any government in any country bears responsibility for the security of its citizens". But Lavrov also stated that the rebels shared the blame for the killings.
On June 26, 2013, the Deputy Russian Foreign Minister said that the Russian naval base at Tartus has been evacuated.
In the United States, President Barack Obama argued that unilateral military action to topple the Bashar al-Assad regime would be a mistake. As the civil war progressed, the United States supported the Syrian opposition against the Assad regime. US criticism of Assad intensified after the Ghouta chemical attack. This led to pressure from both nations, resulting in a Russian-backed agreement that saw the Syrian government relinquish its chemical weapons.
As the Islamic State of Iraq and the Levant (ISIL) took control of large portions of Syria and Iraq, this led to US retaliation within the region. ISIL, which had originated as al-Qaeda in Iraq under the leadership of Abu Musab al-Zarqawi, and ISIL challenged al-Qaeda as the most prominent global terrorist group during President Obama's second term. Beginning in 2014, the Obama administration launched air strikes against ISIL and trained anti-ISIL soldiers, while continuing to oppose Assad's regime. The Obama administration also worked with Syrian Kurds in opposing the ISIL. The strained US relations with Turkey, because the Turkish government alleged that the Syrian Kurds were working with the Kurdish terrorist groups inside Turkey. Russia launched its own military intervention to aid Assad's regime, although the United States and Russia sometimes cooperated to fight ISIL.
In November 2015, President Obama announced a plan to resettle at least 10,000 Syrian refugees in the United States. Obama was criticized for what was termed his "light-footprint" approach to the Syrian conflict. The Syrian Civil War had become a major humanitarian tragedy. Supporters of Obama gave him credit for keeping the United States out of another costly ground war in the Middle East.
On September 15, 2015, in Dushanbe at a meeting of the Russian-led Collective Security Treaty Organization, President Putin called for a united, international effort together with Syria to fight the threat of ISIL. Later that month, in an interview with CBS's '60 Minutes', Putin confirmed that "More than 2,000 terrorist-fighters from Russia and ex-Soviet republics are in the territory of Syria. There is a threat of their return to us. So, instead of waiting for their return, we are helping President al-Assad fight them". Still later in the month, at the United Nations General Assembly, on September 28. 2015, President Putin blamed the conflict in Syria on nations like the United States for "pushing for democratic revolution" in Syria.
On September 30, 2015, Russia launched its first airstrikes against targets in Rastan, Talbiseh, and Zafaraniya in Homs province of Syria. The Russians gave the United States a one-hour advance notice of its operations. The Homs area wa crucial to President Bashar al-Assad's control of western Syria and the move was clearly seen as one supportive of the Syrian President.
On October 13, 2015, Putin criticized the leaders of the American-led intervention in Syria for sending arms to the area that could end up in the wrong hands. He also criticized the American decision not to share with Russia information concerning potential ISIL targets. On 20 October 2015, three weeks into the Russian military campaign began in Syria, Vladimir Putin met Syrian President Bashar al-Assad in Moscow to discuss their joint military campaign which Putin termed to be one "against terrorism" and one for "a long-term settlement, based on a political process that involves all political forces, ethnic and religious groups" in Syria. On February 22, 2016, in Munich, foreign ministers of Russia and the U.S. announced that they had concluded a deal to seek a nationwide "cessation of hostilities" in Syria. By this time, senior U.S. officials had privately admitted that Russia had achieved its central goal of stabilizing the Assad government.

Obama has been criticized for his handling of the Syrian Civil War. History professor David Greenburg, in an article for Financial Post entitled "Syria Will Stain Obama's Legacy Forever", has written:
For now it seems hard to escape the conclusion that in correcting for Bush’s overly aggressive foreign policy, Obama went too far in avoiding confrontations, and that in that halting and hesitant approach he wound up neither strengthening his country’s influence and status nor its power to bring about its ultimate goal of a safer and more peaceful world.
In an article in the Guardian, Simon Tisdall wrote:
By deciding to hand off responsibility, Obama sent another damaging message: that the US, the world’s only superpower, and key allies such as Britain, were not prepared to fight for a free, democratic Syria, no more than they would fight for democracy in support of other Arab Spring revolts. They tried it in Libya in 2011 and quickly recoiled. themselves to counter-terrorism operations and vain calls for peace, and by failing to punish war crimes, western democracies effectively undermined the UN charter, the humanitarian agencies, and international law.