The 900-kilometre (559-mile) border between Turkey and Syria has been riven by tensions since September 2014.
They culminated in an attack on Monday blamed on the jihadist Islamic State group (IS) which left 30 dead on the Turkish side:
Sept 16, 2014: IS attacks Kobane
IS attacks Kobane, Syria’s third largest Kurdish town, on the border with Turkey.
They are driven out in late January 2015 after more than four months of fierce fighting led by Kurdish forces backed by US-led coalition air strikes.
Turkey does not take part in the coalition air strikes but in late October 2014, under international pressure, it allows around 150 Iraqi Kurd Peshmerga fighters to transit with their weapons towards Kobane.
Demonstrations on the Turkish side in which around 30 are killed denounce Ankara’s refusal to intervene in Kobane.
Ankara, which is battling the Kurdistan Workers’ Party (PKK) refuses to see the emergence of an autonomous Kurdish zone in Syria like that in Iraq.
Feb 13, 2015: blast at Suruc
An explosion at a police checkpoint in the southern Turkish town of Suruc close to the Syrian border with Kobane wounds three people, including a policeman.
Feb 22: Turkish incursion into Syria
Turkish troops stage an incursion deep into Syria to evacuate an historic tomb and the soldiers guarding it from IS-controlled territory.
Syria calls the incursion “flagrant aggression” and on May 10 hits out as Turkish Prime Minister Ahmet Davutoglu visits the tomb — which under an international treaty is considered Turkish territory — which has been moved to just 200 metres (650 feet) from the Turkish border inside Syria.
May 16: Syrian helicopter shot down
Turkish fighter jets shoot down a Syrian helicopter that entered Turkey’s airspace in the south.
June 11: Syrian refugees flee
Up to 20,000 Syrian refugees fleeing clashes between Kurdish fighters and IS around Tal Abyad arrive over the space of a week in Turkey, which says it is taking measures to limit the flow.
Turkey, the main host country for Syrian refugees, has already taken in more than 1.8 million since the Syria conflict erupted in March 2011.
June 15: Kurds take Tal Abyad
Syrian Kurdish fighters seize from IS the Akcakale-Tal Abyad border post, which lies on a key supply route to IS’s de facto capital Raqa.
The Kurds deny Ankara’s accusation that they are carrying out “ethnic cleansing” of non-Kurdish populations.
June 25: IS attacks Kobane again
Turkey rejects as “black propaganda” claims that IS militants crossed from Turkey to carry out a deadly bombing inside Kobane.
July 7: rumours of Turkish intervention
Speculation mounts that Turkey could intervene militarily in Syria, after it deploys reinforcements including tanks, anti-aircraft missiles and more troops on the border.
The US special envoy for the anti-IS coalition, John Allen, and Under Secretary of Defence Christine Wormuth, visit Ankara.
Prime Minister Davutoglu rules out any prospect of an immediate intervention, but says Turkey will respond if its security is threatened.
July 12: anti-IS dragnet
In a three-day operation, Turkish security forces detain 45 foreigners trying to enter Syria to join IS from Gaziantep in the southeast.
July 20: twin suicide attacks
A suicide bomber attacks a cultural centre hosting anti-IS activists in the Turkish border town of Suruc near Kobane, killing 30 people in the first attack on Turkish soil blamed on the IS.
A second suicide attack kills two Kurdish fighters in Kobane.