In an exclusive interview with Fox News during his visit to Iraq, Secretary of Defense Ash Carter said there’s “no doubt” the Islamic State ultimately will be defeated – but the bigger question is whether that will lead to a lasting peace.

"We will win, but the important thing is to win and make it stick,” Carter told Fox News, speaking in Irbil, Iraq.

Carter discussed a range of topics, including the recently struck nuclear deal with Iran and Turkey’s military engagement in the region, in the interview.

During his visit, Turkey announced the U.S. may use its Incerlik Airbase to launch strikes against ISIS. Even after the announcement, Carter was cautious.

"This is something that we're going to have to wait and see how it develops ... But I really can't go into details at this time,” he said.  

The next day, underscoring the complexity of the situation, Turkey began launching strikes against the Kurdish PKK  -- a Marxist faction of the Kurds. The PKK is allied with the U.S. in the fight against ISIS, but Turkey considers it a terrorist group. 

On Sunday, Turkish security forces clashed with demonstrators over the air attacks against the PKK.

"Well this is a complicated part of the world, in which there are different communities even within the Kurdish community," Carter said. “That's why nobody can win and lord over everybody else. There has to be inclusive government.”  

There is recent progress in Iraq. Three-thousand U.S.-trained and equipped Iraqi forces are among those who have encircled Ramadi and are poised for an operation to retake the city from ISIS.

Shipments of U.S. weapons are finally arriving to fighters in a timely fashion. But while Carter has not ruled out the use of forward air controllers, he said: "I talked about that with our commanders … here. They have not recommended us taking that step at this time."

Critics in Washington, like Sen. John McCain, R-Ariz., have excoriated commanders for not recommending them.

"Obviously ISIS is winning in Iraq and for you not to be in favor of us having forward air controllers on the ground in some scholastic answer, you know full well as I do -- forward air controllers make the difference,” McCain said.

Despite the current criticism over the approach against ISIS, Carter’s career taken in full has its hawkish sides.

He recommended a preemptive strike against a North Korean intercontinental ballistic missile in the late 1990's. In 2008, he advocated applying military pressure against Iran. Last week at many stops in that volatile region, he said the military option against Iran is very much alive.  

Doug McKelway joined Fox News Channel (FNC) in November 2010 and serves as a Washington-based correspondent. Click here for more information on Doug McKelway