For the most part the United States have kept boots off the ground in the Syrian Civil War, however earlier this month the Pentagon announced that 400 additional US troops are being sent to conduct in-country combat operations.
The United States Military has been involved in the Syrian conflict since September of 2014 when it announced joint airstrikes from the US and its allies. Besides the airstrikes, it was said that there would be no other form of US military involvement, until now. The additional troops include a detachment of the 75th Army Rangers as well as a detachment from the 11th Marine Expeditionary Unit. Their presence became more apparent when the Rangers were seen in a convoy of Stryker armored fighting vehicles and armored Humvees. American officials have said that the deployment of these troops is to help prepare and assist in the fight for Raqqa, which is the self-proclaimed capital of ISIS.
It appears that for the most part, the US forces in country will provide logistical and fire support for Syrian forces assaulting Raqqa, hence the detachment of the Marine artillery unit. At this point there are some fuzziness and concerns regarding what forces will actually seize Raqqa, the American commanders of the operation hope that it will be some combination of Syrian forces and Kurdish Y.P.G. Militia forces, however there is some opposition to this plan.
For those of you who are interested in finding out more information about US forces in Syria or for those who are on the fence about it, I would highly suggest clicking on this link and read this article from Stars and Stripes which explains the details of US operations in Syria.