Turkish policy initially turned a blind eye to efforts by the Islamic State to consolidate its strength across the border. Ankara was reluctant to get involved in direct military action against the militants, despite ISIS links to a series of attacks on Turkish soil – in Reyhanli, Istanbul and Diyarbakir. This stance was criticized both at home and abroad.
The tipping point came in July 2015 when a suicide bombing blamed on the Islamic State killed 32 people in the border province of Suruc; a week later, a Turkish soldier was killed in a cross-border attack.
Recep Tayyip Erdogan’s government rapidly became involved in a war on two fronts: an offensive against the Islamic State and a crackdown on Kurdish PKK rebels.
Turkey arrested Islamic militants at home and launched airstrikes in Syria for the first time in late July. It also allowed coalition fighter jets to use the Incirlik airbase in the south, a move that significantly improved the international coalition's ability to strike ISIS.
An agreement between Washington and Ankara, signed in August 2015, integrated Turkey into the U.S.-led air campaign against the Islamic State.
Turkey has been watching the growing strength of the Kurdish rebels’ armed offshoot, the YPG, across the border in Syria. The YPG has taken the lead in the fight against the Islamic State, driving its fighters from a number of border areas. In the process, it has captured territory next to Turkey’s southern border, creating a semiautonomous region.
This worries Ankara, and critics have accused it of using the conflict as a pretext to resume attacks on Kurdish groups.
A PKK-Turkish cease-fire agreed to in 2013 collapsed in July following fighting in the southeast; the Turkish army claims to have killed some 1,000 rebel fighters since the conflict resumed.
Turkey wants a buffer zone created on the Syrian side of the border – excluding both the Islamic State and the YPG – but has been unable to win the support of the international coalition. Washington remains opposed to the idea.
The United States wants Turkey to do more to control its border with both Syria and Iraq; Turkey remains the most common entry point to ISIS-controlled territory. Potential recruits from Europe and North America now may break up their journey rather than risk attracting unwanted attention by flying directly to Turkey. Others take the land route through the Balkans to Bulgaria or enter via Greece. Traveling by sea is also increasingly popular, as security at Turkish ports is generally lax.
Turkey’s main role is a transit route for Islamic State fighters, but there has been some recruitment within the country, particularly in very conservative areas. The Suruc bombing was carried out by a Turkish national, as was the Diyarbakir bombing in June 2015. Both came from Adiyaman in southeast Turkey, which the authorities see as a potential recruiting ground for ISIS sympathizers.
Meanwhile, Turkey continues to host more Syrian refugees than any other country – at least 1.7 million, although many are not registered. Around a third are housed in 22 government-run camps along the border.
And Turkey may play a vital role in EU efforts to deal with the migrant crisis as the main transit point for arrivals in Europe this year. In an October 2015 summit, European leaders backed proposals that could see Ankara offered a wide range of benefits including 3 billion euros and extensive visa-free travel in return for help stemming the flow of refugees.
Just weeks before Erdogan was reelected as Turkey's president in November 2015, two suicide bombs rocked the capital, killing 128 people at a pro-Kurdish rally, the worst attack of its kind on Turkish soil. The bombings bolstered support for Erdogan, who had pointed the finger at ISIS. Turkey later named one of the bombers as Yunus Emre Alagoz, the brother of the Suruc suicide bomber who ascribed to Islamic State's teachings.