Updated

At least 200 U.S. special operations troops are in Syria advising the Syrian Democratic Forces in their effort to retake the city of Raqqa, the self-proclaimed capital of the Islamic State group.

In recent days, as the U.S.-supported Kurdish and Arab fighters begin to move closer to Raqqa, there have been persistent questions about how close American troops are getting to the front lines.

When the mission was initially announced last October, the White House ruled out a combat role and made it clear that the commandos' job was not "to lead the charge to take a hill but rather to offer advice and assistance to those local forces." But in recent days photos have shown them in locations that appear to be closer to the fight.

Questions and answers about their role:

Q: What exactly are the American forces doing?

A: The Obama administration has authorized 300 U.S. troops to go into Syria to coordinate with the local Syrian rebel forces, providing training, combat advice, operational planning and guidance. According to Col. Steve Warren, U.S. military spokesman in Baghdad, the force often refines the rebels' battle plans and help them coordinate their ground movements with U.S. and coalition airstrikes.

They are not fighting alongside the rebel forces in direct combat.

Q: Are they on the front lines?

A: The Pentagon insists they are not. But military officials acknowledge that there is no real line and that U.S. troops are sometimes closer to the fighting than at other times. U.S. troops can only go where they believe "enemy contact is unlikely." Warren said they analyze where they can go and ensure that they are not likely to come in contact with enemy fighters.

The rule of thumb is to position themselves one terrain feature away — which could refer to a hill, a valley or woody area, Warren said.

Q: Then how far away are they from combat?

A: It depends. Sometimes miles, other times much closer. Last weekend, at a base in Syria where U.S. military advisers are working with local forces, one American told visiting reporters that he had been in a forward location with the rebels as they fought to retake the town of al-Shaddadi. The American was speaking under ground rules that did not permit the public release of his name or exact military affiliation.

Warren said there is no specific distance required and it usually depends on the terrain. In wide-open areas they would be further back than they might be in places where there is more cover.

As an example. U.S. forces in Iraq are also serving as advisers and are not in combat. But Chief Petty Officer Charles Keating IV, a Navy SEAL, was killed in May when, as part of a quick reaction force, he went to the aid of U.S. advisers who got caught in a gun battle. They had gone to meet with Kurdish Peshmerga forces and came under attack by Islamic State fighters.

Q: Have they been engaged in combat in Syria yet?

A: Warren said that while he may not know what happens out in the field every minute of the day, "to my knowledge, no, at this point none of them have been engaged" in combat in Syria.