The history of US-policy on Syria is as old as the history of modern Syria itself. Even when today's country was still a part of the Ottoman Empire, the US sent a diplomatic envoy to Damascus - and Washington has been influencing the region's politics ever since:
A former colony themselves, the United States quickly got involved in Syria's push for independence. President Harry S. Truman opposed French endeavors to regain the League of Nations mandate for Syria after World War II. With support from the US, Syria managed to advance its own sovereignty and became one of the original signatories of the UN Charter in 1945.
1957: A CIA-backed coup
The first diplomatic crisis came just 10 years later, when Syria got caught up in disputes over oil and hegemony between the US and the Soviet Union. Backed by the CIA, the Syrian military ousted democratically-elected President Shukri al-Quwatli in 1949. After regaining power in 1955, al-Quwatli turned to pro-Soviet Egypt. A second attempt by the US to overthrow him failed. Both countries then put diplomatic relations on hold. For a brief period, Syria merged with Egypt to form the United Arabic Republic.
1967: Six days of war, 20 years of conflict
It was a war which wouldn't last a week yet shaped the Middle East for years to come. From June 5-10, 1967, fighting broke out between Israel and the Arab states Egypt, Jordan and Syria. It was the third military conflict between the two sides since the formation of Israel. The Six-Day War ended with Israel leaning closer to the US, after receiving Washington's support in the conflict. As the Soviet Union provided arms to Egypt and Syria, the Arab League took a hard line on Israel: no recognition, no negotiations, no peace.
1990: Gulf War allies
After Iraq marched into Kuwait in the summer of 1990, the US quickly spearheaded a UN-wide military coalition - including Syria - to come to the aid of the small Middle Eastern state. The military campaign saw numerous air strikes and ground troop deployments beginning in January 1991 and lasting until Iraq's surrender that March.
No compromise for Clinton
Under Bill Clinton, the fragile cooperation between Washington and Damascus failed again: As the US President was trying to reach a Middle East peace deal through the Oslo accords, he invited Syria, Egypt and Lebanon to join the talks. But various efforts through his two-term presidency ultimately failed. Among the reasons was opposition from Syrian President Hafez al-Assad, who ran the country from 1971 until his death in 2000.
2002: A veto for the Iraq war
The US took an even more direct role in the Middle East after the 9/11 terror attacks. At first, Syria was spared from President George W. Bush's "rogue state" rhetoric. As a sign of good will, Damascus provided Washington with information about extremists networks. In return, it demanded support for its intentions to reclaim Lebanon as a protectorate again.
But the US instead dove head-first into the Iraq War. Syria opposed the move on the UN Security Council. New Syrian ruler Bashaar al-Assad, the son of Hafez, went so far as to ignore sanctions against Iraq, expanding its trade volume up to $3 million.
The action left the US indecisive over how to best deal with Syria. The State Department wanted to win over Damascus as a war ally, but the Pentagon opposed that approach due to Assad's ties with local terror groups. Following Lebanese Prime Minister Rafik Hariri's assassination in 2005, Washington pulled its ambassador out of Damascus and accused Syria of being behind the attack.
Obama: Diplomacy and airstrikes
When civil war broke out under Assad in 2011, Syria once again became a US foreign policy priority. President Barack Obama tried to call the regime to account with a row of sanctions. At the same time, he pursued diplomatic dialogue by sending a new ambassador to Damascus in 2013 - the first in eight years.
At the beginning of the Syrian conflict, then-Secretary of State Hillary Clinton claimed a military offensive in the country would be out of the question. But in 2013, the US began arming Syrian rebels amid concern over a chemical weapons attack.
Since 2015, the US has been conducting airstrikes in Syria as part of its effort to combat the so-called "Islamic State" militant group. At the UN Security Council and at Syrian peace talks, the US, along with other Western states, and Russia are the key negotiation partners trying to bring an end to the conflict.