On 22 September 2014, the United States officially intervened in the Syrian civil war with the objective of fighting the Islamic State as part of Operation Inherent Resolve in the international war against the Islamic State. The U.S. also supports the Syrian rebels and the Kurdish-led Syrian Democratic Forces opposed to both the Islamic State and Syrian president Bashar al-Assad.
Shortly after the start of the civil war in 2011, the Obama administration placed sanctions against Syria and supported the Free Syrian Army rebel faction by covertly authorizing Timber Sycamore under which the Central Intelligence Agency (CIA) armed and trained rebels. Following the Islamic State's occupation of Eastern Syria in August 2014, the United States conducted surveillance flights in Syria to gather intelligence regarding the Islamic State. In September 2014, the United States-led coalition—which involves the United Kingdom, France, Jordan, Turkey, Canada, Australia, and others—launched an air campaign against the Islamic State and al-Nusra Front inside Syria.
The U.S. missile strike on Shayrat Airbase on 7 April 2017 was the first time the U.S. deliberately attacked Syrian government forces during the war, and marked the start of a series of direct military actions by U.S. forces against the Syrian government and its allies via airstrikes and aircraft shoot-downs, mainly in defense of either the Syrian Democratic Forces or the Syrian Free Army opposition group based in al-Tanf. In mid-January 2018, the Trump administration indicated its intention to maintain an open-ended military presence in Syria to accomplish U.S. political objectives, including countering Iranian influence and ousting Syrian president Bashar al-Assad. However, on 19 December, President Trump unilaterally ordered the withdrawal of the 2,000–2,500 U.S. ground troops in Syria at the time, which was to be completed in 2019. With proliferating concerns over a potential power vacuum, the U.S. announced on 22 February 2019 that instead of a total withdrawal, a contingency force of around 400 U.S. troops would remain garrisoned in Syria indefinitely, and that their withdrawal would be gradual and conditions-based, returning to a policy of open-ended American military presence in the country.
In 2019, the coalition saw decisive results in its intervention against the Islamic State; the terror group lost its last remaining territory in Syria during the battle of Baghuz Fawqani and its leader Abu Bakr al-Baghdadi died during a U.S. special forces raid in Idlib in October 2019. The Trump administration ordered all U.S. forces to withdraw from Rojava in early October ahead of a Turkish incursion into the region, a controversial move widely seen as a reneging of the U.S.'s alliance with the SDF in favor of NATO ally Turkey. However, by November 2019, U.S. troops instead repositioned to eastern Syria, reinforcing their presence in the al-Hasakah and Deir ez-Zor governorates, with the subordinate mission of securing SDF-controlled oil and gas infrastructure from the IS insurgency and the Syrian government. On 23 November 2019, the head of U.S. Central Command stated there was no "end date" on the U.S.'s intervention in Syria.
As of February 2021, there are around 900 U.S. soldiers operating in Syria, according to the U.S. Department of Defense.
Background
United States diplomatic cables leaked by WikiLeaks have been seen as showing that regime change in Syria may have been a covert foreign policy goal of the U.S. government in the years leading up to the civil war, even during the period when President Barack Obama was publicly engaging with Syrian president Bashar Al-Assad. A 2006 memorandum by U.S. diplomat William Roebuck of the embassy in Damascus stated:We believe Bashar's weaknesses are in how he chooses to react to looming issues, both perceived and real, such as...the potential threat to the regime from the increasing presence of transiting Islamist extremists. This cable summarizes our assessment of these vulnerabilities and suggests that there may be actions, statements and signals that the USG can send that will improve the likelihood of such opportunities arising. These proposals will need to be fleshed out and converted into real actions and we need to be ready to move quickly to take advantage of such opportunities. Many of our suggestions underline using Public Diplomacy and more indirect means to send messages that influence the inner circle.According to Seymour Hersh and activist Robert Naiman, Roebuck, who went on to be charge d'affairs of the Libyan embassy under Obama, also considered the advantages of promoting religious sectarianism in Syria.