Turkish Prime Minister Binali Yıldırım declared on Sunday that Turkish army and rebels belonging to the Free Syrian Army (FSA) finally secured 95 km of Turkish-Syrian border which were under the control of the Islamic State (IS).
Since the beginning of the Syrian civil war, this border segment has served as a supply corridor for terrorists, allowing goods, weapons and foreign fighters to enter Syria.
Turkish soldiers and FSA rebels are fighting to secure the inner part of the area. Their main objective is to move south and reach the city of Al-Bab, an IS stronghold.
The Free Syrian Army was created by a group of army deserters in 2011 in opposition to Syrian President Bashar al-Assad. During the conflict, the group fragmented and it is reported that many of its fighters joined Islamic State's ranks.
The Turkish and FSA offensive is part of Operation Euphrates Shield, started on August 24 from the border city of Jarablus, on the western banks of the Euphrates.
The river is the longest of western Asia. It starts from Turkey, flows through Syria and Iraq before flowing into the Persian Gulf. Since ancient times, it represents a vital waterway to move men and goods throughout the whole of West Asia.
The majority of its Syrian flow is currently under IS control but the loss of Jarablus prevents them access from Turkey, depriving them of a fundamental entry point.
It remains unclear why Turkey did not secure this area before.
The border line running from the city of Jarablus to the city of Al-Rai stands between the Syrian region of Rojava, a Kurdish-controlled area, and the Kurdish constituency of Afrin. Both these locations are under the control of the Yekîneyên Parastina Gel (YPG), the People's Protection Unit, a Kurdish army which is fighting on the ground since 2012 against the Islamic State.
YPG is an official US ally, its members have been trained by American military personnel. It has the characteristics of a guerrilla force which relies on surprise and speedy action and has a significant component of women fighters within its rank and file.
Its main task is to enter cities and villages after US airstrikes to clear the Islamic State's pockets of resistance.
The Turkish government considers the YPG a terrorist organisation and Prime Minister Binali Yıldırım stated that they will not accept the existence of a Kurdish region right across their border.
"We will never allow an artificial state in Northern Syria," he said on Sunday.
This denial resulted in a two-decade long Kurdish insurgency characterised by violence on both sides. The European Court of Human Rights has reported thousands of human rights violations, including executions, torture, forced displacements, village destructions and arbitrary arrests perpetrated by the Turkish government against the Kurdish population.
Ankara believes that the YPG is just its extension and that a Kurdish stronghold, right across the border, could give a new lifeline to the Kurds living in Turkey. Turkey is scared that it will bolster their separatist spirit.
Attacking the YPG means attacking a formal US ally but Turkey belongs to NATO. This puts Washington in a tricky situation.
During the first phase of Operation Euphrates Shield, the Turkish army declared to have killed 25 “Kurdish terrorists,” an action that has been judged by the US Department of State "unacceptable and a source of deep concern."
The United States "were not involved in these activities, they were not coordinated with US forces, and we do not support them," said Pentagon spokesman Peter Cook.
When Turkish forces and Free Syrian Army rebels entered the city of Jarablus, they ordered the Kurds to retreat to the eastern bank of the Euphrates river, a request that was immediately supported by the US.
The YPG high command has sent an official Tweet, requesting its fighters not to fight back and reminding them that the true enemy is the Islamic State and not Turkey.
It is, nonetheless, unlikely that the situation will remain stable for long. Even if Kurds are not yet responding, they make no bones about their intention to remain in Rojava after – and if – the war is over.
President Erdogan is also clear about his programme. He said in a statement that the offensive would continue until "the threat of Islamic State and YPG/PKK is over."
US defence secretary Ashton Carter said he had appealed to both sides not to fight. "That's the basis of our cooperation with both of them, specifically not to engage one another," he said.
Ankara denied the existence of any official ceasefire and does not seem to be willing to change its mind. During a meeting with US President Obama, the first after the coup, on Sunday at the G20 summit in Hangzhou, President Erdogan said, “We have to embrace the same stance against all terrorist organisations around the world.” “Our hope is never to see a belt of terrorism, a corridor of terrorism emerging in or around our region.”
“There is no good terrorist or bad terrorist; every kind of terrorism is bad,” Erdoğan said after the meeting with Obama, the Turkish state-run Anadolu news agency reported.
Operation Euphrates Shield is a stress test for US-Turkey relations which are at its lowest after the failed Turkey coup and the allegations made by President Erdogan of a possible US role in it. Ankara has been demanding the extradition of Fetullah Gulen, the Pennsylvania-based cleric who they believe to be the mastermind behind the coup.