Will a Turkish border deal block IS recruits? By Frank Gardner

BBC Security correspondent Published duration 28 August 2015

image copyright Getty Images image caption Many Western recruits to IS travel to Syria via Turkey

Fifteen months after the jihadists of so-called "Islamic State" overran Mosul and announced their controversial "caliphate", measures are in train that could seriously disrupt their supply of recruits.

In co-ordination with Washington and other NATO allies, Turkey is now considering imposing a buffer zone along part of its 700-mile common border with Syria.

The stated aim is to deny access by would-be jihadists to IS-controlled areas of northern Syria.

A US military spokesman recently claimed that the last 12 months of Coalition airstrikes had "killed around 10,000 IS fighters" , a dubious metric for measuring military success and a hard claim to verify in this fluid conflict.

But even if true, western intelligence officials believe that IS has been able to regenerate its supply of recruits faster than it is being depleted.

So with IS still occupying largely the same area of Iraq and Syria that it did a year ago, how will the proposed Turkish border controls affect its flow of recruits?

Turkish-Syrian border

The main crossing route for would-be jihadists looking to join IS.

The normal method is to fly into Istanbul, no visa required for Europeans, meet up with a facilitator, take a bus to a town close to the Syrian border then use local smugglers to sneak across into IS-held territory.

An estimated 2.5 million Britons visit Turkey every year so at least 1,000 British jihadists and thousands more Europeans are believed to have evaded police and intelligence surveillance to cross into Turkey and reach IS territory.

Most of the 588-mile (900km) Turkish-Syrian border is controlled on the Syrian side by YPG (Kurdish Peoples' Protection Unit) forces, who are opposed to IS.

Turkey is hoping that a 60km buffer zone will close off the remaining IS-controlled length of border to the west.

This may slow down the flow of incoming European jihadists to IS, already down from its peak in 2013, but in practice loopholes in the border are likely to remain.

Syrian-Iraqi border

Since June 2014 IS jihadists have taken control of most of the main crossing points between Syria and Iraq, bulldozing away the checkpoints and declaring an end to the colonial-era 372-mile (600km) border with the Twitter hashtag SykesPicotNoMore.

Although frequently targeted by coalition airstrikes as they cross between Syria and Iraq, IS does have freedom of movement over much of this border.

However, to join IS this way any would-be recruit would have to first get themselves to Iraq and then negotiate their way through either Kurdish or Iraqi government and militia territory, so it is not an attractive option.

Jordanian-Iraqi border

image copyright Frank Gardner image caption Traffic through Jordan's desert border with Iraq has slowed

Jordan's desert border with Iraq at the Karama crossing once buzzed with busy traffic.

Lorries thundered up the highway from Aqaba to Baghdad but since the insurgency in Iraq accelerated, the traffic has slowed to a trickle.

Jordanian military and police units patrol the border with Iraq's troubled Anbar province and when we visited in May there was no traffic at all.

Iraqi government forces are in control of their side of the border although IS occupies the towns of Falluja and Ramadi further down the road.

Jordanian-Syrian border

Jordan closed its last crossing point, the Nassib crossing, on its 246-mile (397km) border with Syria in April 2015.

image copyright Frank Gardner image caption The Jordan-Syria border is now closed

When the Syrian conflict first erupted in 2011 Jordan opened its borders to thousands of refugees fleeing the fighting.

But since then Jordan, which is not a rich country, has struggled to cope with the influx.

The Zaatari refugee camp, close to the Syrian border, is now dubbed 'the fourth biggest town in Jordan'.

Jordan has its own internal problems with Islamist extremists, notably in Ma'an and Zarqa, so it has moved to stop the flow of any jihadists across the border into Syria.

Lebanese-Syrian border

If Turkey blocks most of its border with Syria to IS jihadists then Lebanon could well become the sole remaining option for them. Lebanon has a 250-mile (403km) border with Syria, much of it mountainous.

image copyright EPA image caption Hezbollah fighters are thought to be helping the Assad regime

This is frequently traversed by both the Iranian-backed Shia fighters of Hezbollah , who are helping to shore up the regime of Syria's President Bashar Al-Assad, and by Sunni jihadists fighting them.

IS enjoys some local support on both sides of the border in the far north-east corner of Lebanon where it has occasionally attacked Lebanese army positions.

But Lebanon would still present recruits and emigrants to IS with a far less attractive access route than Turkey.

What this means

IS may already be ahead of the game here.

image caption Syria border crossings

In recent months its leadership in the Middle East has been advising followers in Europe to stay put and carry out attacks at home, rather than risk arrest and incarceration by making the journey out to Syria.

The net effect of this, assuming coalition airstrikes continue, could be to see IS numbers in its core "caliphate" heartland slowly reduce, though not necessarily to a level where its operations are seriously affected.

But conversely, the group is likely to intensify its already active propaganda campaign through social media, appealing to jihadists in both Europe and other parts of the Arab world to launch attacks.