Peter Bergen is CNN's national security analyst, a vice president at New America and a professor of practice at Arizona State University. He is the author of "United States of Jihad: Investigating America's Homegrown Terrorists."

(CNN) As US-backed Iraqi forces move closer to wresting control of Mosul from ISIS, plans are already underway for striking the heart of the terrorist group's would-be "caliphate," the Syrian city of Raqqa.

Both cities are the major objectives in a new and largely untested kind of American military strategy to defeat ISIS' terrorist army in the Middle East. Rather than commit substantial land forces, the United States is providing Special Forces, intelligence resources and substantial air power to Iraqi and Syrian fighters on the ground.

The last time the United States used this approach in a substantial manner was a decade and half ago in Afghanistan, where a similar combination of US Special Forces working with their Afghan allies on the ground combined with large-scale American airpower led to the overthrow of the Taliban in Afghanistan in the months after 9/11.

After some of the sweeping rhetoric of American leaders failed to produce a lasting peace in Iraq during the Bush administration and after the Obama administration's failure to abate the Syrian civil war, a new realism has set in among America's politicians and the generals who work for them. Gone is the talk about wiping out terrorism for good or building Western-style democracy.

To get a sense of how this strategy is unfolding, I've traveled over the past week with the architect of the war against ISIS, Gen. Joseph Votel, the commander of US Central Command. During the trip we traveled to Afghanistan and Iraq and met with many of the generals working under Votel's direction. The war in Afghanistan appears to have ground to something of a stalemate with the Taliban, while in Iraq and Syria it's clear the momentum has moved decisively against ISIS.

Votel, 58, previously led US Special Operations Command and the secretive Joint Special Operations Command, which was the unit that killed Osama bin Laden in 2011, shortly before Votel assumed its command. That Votel is in charge of the wars in Afghanistan, Iraq and Syria is itself unusual, as it's the first time a Special Operations veteran has been put in charge of all those wars, underlining the Obama administration's increasing reliance on Special Operations Forces.

Votel, a native of Minnesota and a big Vikings football fan, sat down with me on Thursday at a US base in the Middle East and also on his plane on Friday to discuss how that campaign is going, from the commencement of major combat operations to take back Mosul, the second largest city in Iraq, from ISIS, to the incipient US operations around Raqqa, ISIS' de facto capital in Syria, to ISIS' plans to transform from a physical caliphate to a virtual one, and the continued threat posed by al Qaeda's affiliate in Syria. The conversation has been edited for clarity.

Bergen: Has the campaign against ISIS in Raqqa already started?

Votel: We have been doing preparatory stuff against Raqqa and Mosul for a long time, long before we said "the assault on Mosul has begun." We have taken out 36 ISIS leaders in the Mosul area; to me that is part of the preparation phase.

So we have to think about this in the same way in Raqqa. If we see ISIS leaders in Raqqa we will take them out. To that extent, we can legitimately say, "Yes, we are doing operations in Raqqa."

The importance of Raqqa is that is where ISIS plans their external [terrorist] operations. That is what is driving us to get on this as quick as we can, because this is where the plotting takes place. That doesn't mean we necessarily know that there is a specific plot we are trying to disrupt now or in a couple of weeks, but Raqqa is recognized as the financial, leadership and external ops center of the Islamic State, so that's what makes it important.

Bergen: Abu Bakr al-Baghdadi, the leader of ISIS: Is he still running the show? Where is he now? And is there a succession plan if he were to be killed?

Votel: My presumption is he is still running the show. I don't know that we have any specific location. If we did we would be actively going against him. That said, we are actively looking for all leads that would allow us to target him. I presume he has developed a succession plan. He certainly has watched a number of his leaders be targeted over time, and I think that he has had to pay attention to some of the hollowing out of his leadership that has taken place over the past several months.

Bergen: Obviously, taking one leader out doesn't make a big difference, but when you have killed 36 leaders as you have done around Mosul, or the scores of other leaders and key officials you have killed in ISIS writ large, that begins to have effects?

Votel: It does. It begins to eliminate some of their resiliency. It begins to disrupt their careful organization, so that they have leaders having to do multiple things. It disrupts their timing; it disrupts their decision-making process and it upsets how they manage their resources and provide directions. It does have an impact. Those numbers of leaders you cited that we were able to target in the Mosul area will be helpful to the overall campaign.

Bergen: What does next year look like for ISIS?

Votel: What I'm concerned about is that as the physical caliphate is dismantled we have to be concerned about the virtual caliphate. This is an organization that has demonstrated a high degree of technical capability, Internet savvy, a real ability to propagate its ideology through social media that really resonates with young populations. That was not a factor in the past.

When you look at Dabiq magazine [ISIS' English language webzine] this is a high quality publication. This isn't done in an ad hoc fashion. I read Dabiq every time one comes out. They are generally high quality. The quality of the English writing is good.

ISIS does recognize that the physical caliphate is under enormous stress and they have begun to prepare for this more virtual approach.

Bergen: At the end of the day you can be radicalized online, but you can't get real training online. There is a big difference between a physical caliphate and a virtual caliphate, right?

Votel: Absolutely, but they don't have to be successful every time. They only have to be successful one out of 10 times and it feeds their narrative very effectively.

Bergen: What can be done about the virtual caliphate?

Votel: We have to continue to physically go after those social media production nodes. We have to continue to enlist the broader Muslim world and get credible voices that can offer alternatives to this.

Bergen: ISIS seems to have a somewhat incoherent strategy, first creating a physical caliphate, then attacking the West and killing Americans. But by attacking in the West doesn't that undermine their main goal of retaining a physical caliphate?

Votel: In the beginning ISIS certainly thought that the physical caliphate was the way to go, but as they have come under pressure we are seeing people conducting attacks in the West, whether they are influenced or inspired by ISIS, which is more than willing to take credit for these attacks.

They're beginning to view the "citizenry" of the caliphate much more in a virtual manner than in the physical manner. You can be a member of the group wherever you are. You can be an e-citizen.

They certainly raised the focus on themselves because of the attacks in the West. That has given more impetus for coalition countries to attack them and the caliphate being dismantled.

Bergen: The major attack on ISIS in Mosul over the past week or so involving both the Iraqi army and Kurdish militias who often don't have the same goals has gone well so far. Was that surprising?

Votel: To some extent the Islamic State has been a unifying factor. That is the one thing everyone can agree on. They may have lots of differences; the one thing they don't differ on is the threat the Islamic State poses. With the strong support of the coalition, the major parties -- the Kurds and the government of Iraq and the local tribes -- have all seen that before they go on to address their political issues they have to address this common threat.

Bergen: Do you think Iraqi Prime Minister Haider al-Abadi -- who leads a largely Shia government -- has internalized the message that his government must have some kind of political accommodation with Iraq's Sunnis if we aren't going to see a son of ISIS or a grandson of ISIS emerge down the road?

Votel: I think he personally has internalized it. I couldn't make a comment if he has done it across the government as I don't have that particular perspective. I know from my interactions with the Prime Minister, which are routine, that he clearly sees a need for an inclusive approach going forward.

Bergen: He has expressed that to you?

Votel: Yes.

Bergen: ISIS is a symptom of some deep problems: Sunni-Shia rivalry, Iran-Saudi rivalry in the region, and the collapse of Arab governance. Do you think five years from now you will be fighting a son of ISIS or a grandson of ISIS? Will there be other iterations of ISIS?

Votel: I hope in five years we won't be fighting a son of ISIS, but these terrorist groups don't just evaporate. There will be remnants and they will have to be addressed. What the coalition can do is to help the Iraqi security services to develop capabilities. Ultimately they will have to own this.

Bergen: What happens in Syria after the defeat of ISIS?

Votel: The Islamic State won't completely evaporate; there will be a need to address that with our indigenous partners on the ground. Removing ISIS as a physical caliphate, in and of itself, probably will not be enough to be the trigger that brings stability to Syria, but it's a necessary precondition for stability that this group is neutralized.

Bergen: What is your plan for the many thousands of fighters from around the Arab world and from Europe who are now fighting with ISIS that may not be killed on the battlefield? Is there a plan to prevent them from leaving for the West or elsewhere?

Votel: This is a real challenge; in Iraq there is a legitimate government that they can be turned over to and there is a justice system that can deal with them. It becomes a little more tricky in a place like Syria.

Bergen: Are you concerned about the al Qaeda affiliate known as Nusra in Syria?

Votel: It's very strong, very powerful. It has taken a long-term view, and it poses a long-term threat to the region and beyond. They are focused right now internally in Syria, but at their core they are al Qaeda and so I think they have longer and broader goals. In terms of size, it's several thousand fighters and is a very capable organization that has demonstrated success in its operations against the Assad regime.

Bergen: Is there a possibility that what remains of ISIS joins Nusra despite the fact that right now they are at odds with each other?

Votel: I don't see anything now that would suggest that, but these organizations are highly adaptive. There is no way of predicting what their relations are after this. We have to consider the possibility that what remains of ISIS will try and join up with other like-minded groups.