U.S. troops have been on the ground in Syria for over a decade. Here's the back story and present situation after the deadly Islamic State attack | Fortune

"The United States has had troops on the ground in Syria for over a decade, with a stated mission of fighting IS. While not part of its official mission, the U.S. presence has also been seen as a means to hinder the flow of Iranian and Iran-backed fighters and weapons into Syria from neighboring Iraq. The number of U.S. troops in the country has fluctuated and currently stands at around 900. They are mainly posted in the Kurdish-controlled northeast and at the al-Tanf base."

"Wary of getting bogged down in another costly and politically unpopular war in the Middle East after its experience in Iraq and Afghanistan, Washington sent support to rebel groups but at first avoided direct military intervention. That changed after the rise of the IS, which carried out sporadic attacks in the U.S. and Europe, while in Iraq and Syria, it seized territory that was at one point half the size of the United Kingdom."

U.S. forces have been in Syria for over a decade with a stated mission to fight IS and to hinder the flow of Iranian and Iran-backed fighters and weapons into Syria from neighboring Iraq. Troop levels have fluctuated and currently number around 900, mainly posted in the Kurdish-controlled northeast and at the al-Tanf base near the Iraq and Jordan borders. The U.S. began an air campaign in 2014 and deployed ground troops in 2015 to partner with Kurdish-led forces after IS seized large swaths of territory and carried out attacks in the U.S. and Europe.

Read at Fortune