size of Great Britain and a population of 11 million people. But today it's lost

about 60% of that and its population is down to about two and a half million.

It's the result of fighting its enemies on all sides.

To the west and north, ISIS is fighting armed rebel groups and the Russian-backed Syrian military and it's allies.

It's also fighting Turkish troops and US-backed Kurdish forces in the north.

And to the east and south, there's the US backed Iraqi army. It was this Iraqi

army that delivered the latest blow when they took over Isis's biggest city Mosul.

The group's capital in Iraq. It was a symbolic loss. Mosul is where the group

declared a Caliphate, or Islamic territory, in 2014. This set them apart

from other terrorist organizations. They weren't just a network of jihadists

strung out across several countries like Al Qaeda. They governed actual territory

which they called the Islamic state. Now with the loss of Mosul, the fall of this

ISIS Caliphate seems imminent. So what happens when Isis is gone?

Problem number one is that these fighters are going to want to go home. So in 2014 when

ISIS captured a huge swath of territory in Iraq and Syria, tens of thousands of

foreign fighters came from all over the world to join the caliphate.

According to UN estimates as of July 2016 there are upwards of 30,000 foreign

fighters. So most of these fighters came from countries like Tunisia, Morocco,

Jordan, Saudi Arabia, but hundreds also came from countries like Belgium, Germany,

the UK, and even a few dozen from the United States. So these fighters were

drawn to ISIS for all sorts of different reasons, but a big one was that it had

actual territory and was supposed to be building a Caliphate based on its own

extreme interpretation of Islamic law. ISIS propaganda pushed this narrative in

flashy violent videos and magazines online encouraging people from all walks

of life, not just fighters, to come and help build this glorious Islamic state.

And the people who came were not just young men, they weren't just fighters,

there were women children and even families who came as well. But now as

ISIS territory shrinks and the state that they tried to build collapses,

anyone who survives will have to find somewhere else to go... and that's a major

problem because many of these people are now indoctrinated, there now

well-connected and they're capable of carrying out deadly terror attacks.

A similar dynamic actually happened back in the 1980s in Afghanistan. So thousands

of foreign fighters flocked to Afghanistan to help the Afghan mujahideen

fight the Soviet invasion. After the Soviets left a lot of these

fighters dispersed to various different theaters of jihad including Bosnia,

Chechnya, Somalia, Sudan, and elsewhere. These fighters ended up forming a loose

network of transnational jihadists, most of whom had links to Osama bin Laden and

al-Qaeda, thanks to their time fighting in

Afghanistan. And some of them actually went on to carry out attacks against the

West, including attacks against the United States. So the worry now is that

ISIS fighters will do something similar but this time they might actually make

it home to places like Europe and launch attacks there.

So the second problem is what to do with the US military after ISIS falls. Right now the US is helping

local forces in Iraq and Syria to defeat ISIS. There are currently

around 1,000 US troops in Syria and around 6,000 US troops in Iraq. Mosul

which was ISIS's capital in Iraq has fallen and right now the US is helping

Syrian local forces to defeat ISIS in Raqqa its so-called capital there. So as

those two cities fall ISIS has been spreading out to rural areas. The Trump

administration had two choices. Option one is to keep the US troops there which

would lead them in harm's way. Or option two is to bring them home, which

increases the risk that the region breaks out into war again. Option 1 is a

big political risk for Trump. He promised during the campaign that he would not

get involved in foreign wars that he would actually invest American money and

time and jobs and research in the United States. And so if Trump were to keep

troops in the region it would be admitting that he's going against the

political philosophy he espoused during the campaign and currently during his

presidency. Option two is definitely also a risk for Trump if US troops were to

leave that opens a space for sectarian violence to break out in the region.

Let's take a look for example at what happened in 2011 the Obama

administration took most of its troops out of the region that gave the Shiite

government in Baghdad the space to crack down on Sunni population throughout the

country and ISIS took advantage of that. ISIS was seen as the defender against

the Shiite government and was able to gain support and allow for its rise.

So while it doesn't necessarily mean that it's troops leave an ISIS type

group or ISIS 2.0 itself would grow out of that absence of US troops but that risk

certainly exists.

A deadly California shooting rampage. A lone gunman to pledge allegiance to ISIS. Both incidents carried out by so-called lone wolves

Problem number three is ISIS moving from a place to an idea. Up until now ISIS had

one goal: defend the territory it already had in Iraq and the territory already

had in Syria. The problem is on the verge of losing both. When that happens

ISIS goes from being the kind of place people go to fight to being the idea

that people fight for. It's an idea that's compelling it's an

idea that its followers are willing to kill for and as followers are willing to

die for. When they first came to power people thought it's a group that has its

own territory, it wants to control that territory, but it's not al-Qaeda, it's not

a terror group that wants to carry out attacks outside of its borders in the

West. That was proven tragically wrong in October of 2015.. "this is the bomb ISIS

claims they use to bring down the Russian passenger plane over the Sinai

Peninsula." In their online magazine they posted photos of the bomb that they said

had been used to blow up the plane. And that was a reminder for was about to

come. A wave of ISIS attacks that have killed hundreds of people in London, in

Paris, and in Nice. And have inspired attacks that have killed dozens here at

home in California and in Orlando. It's worth remembering that these are not

always attacks carried out by people who are part of ISIS. In many cases these are

people who are radicalized in the countries where they lived and that's

the danger of the idea. Take what happened in San Bernardino, California

where a married couple killed 14 people. Or in Orlando where a single shooter

killed 49 people. In both cases ISIS claimed responsibility but in both cases

there is no connection between those people and Isis. They got radicalized

over the Internet Isis has known that propaganda matters

and ISIS is really good at it. It has people all over the world who use English

language Arabic language to have Facebook pages and Twitter accounts that

are full of incredibly slickly produced videos. They're really compelling and if

you're someone predisposed to have that worldview, they can push you over the

edge from just thinking that's an idea worth killing for,

to actually killing for it. ISIS takes it so seriously

that it refers to these people as media operatives and says those media

operatives are carrying out a form of martyrdom akin to killing, to literally

killing for the cause. And at the end of the day that's the hardest thing about

ISIS. It can be beaten on the ground in Iraq and Syria. It is

being beaten on the ground in Iraq and Syria, but it's going from being a place

to an idea. And it is impossible, impossible to defeat an idea.