[2] The failed Turkish-U.S. arrangement was replaced on 22 October 2019 with the separate Second Northern Syria Buffer Zone, negotiated between Russia, Turkey and the Assad government.

This has led Turkey to intervene twice against the group by 2019, first by invading northern Syria to prevent the linking of SDF-held areas and later by launching a full-scale attack against the SDF in Afrin.

[7][8] At the same time, US President Donald Trump expressed his intention to disengage from the Syrian civil war, initially ordering all US personnel in Syria to be withdrawn[9] before later deciding to maintain a small contingent, at the behest of his military advisors.

During summer of 2019, Turkish president Recep Tayyip Erdoğan announced that Turkey could "no longer wait" and would not tolerate continued SDF presence along the Turkish-Syrian border.

[18] He stated that if the US did not agree to a deal that would remove the SDF from those areas, Turkey would unilaterally launch a full-scale invasion against SDF-held territories east of the Euphrates river, establishing a Turkish-occupied "security zone" along the border – something that US leadership viewed as "unacceptable".

[19][20] With the Turkish army massing along the border, the Trump administration decided to enter into negotiations with Turkey over establishing a "safe zone", which would fundamentally address the SDF presence in Northern Syria.

[63] On 10 September, Turkish Foreign Minister Mevlüt Çavuşoğlu accused the United States of "stalling" the implementation of the zone and reasserted the threat that Turkey would unilaterally invade Northern Syria, if it deemed it necessary.

[68][69] On 12 September, the U.S. military was reported as considering the proposition of sending about 150 additional troops to Northern Syria in an attempt to "reduce tensions" between the SDF and Turkey.

[87] On 5 October, the Turkish president Erdoğan warned that a full-scale invasion of Northern Syria could start that same or following day, after defining the joint U.S.-Turkish ground and air patrols as "a fairy tale".

Trump's sudden approval of a Turkish incursion was seen as a reversal of the objectives of the Buffer Zone agreement and was received controversially within the United States.

[109][110] Masoud Barzani, senior politician in Iraqi Kurdistan Regional Government, urged Russia to intervene in the crisis in order to prevent "further suffering and pain of the Kurdish people in Syria".

[118] The conservative American news outlet Washington Examiner described the establishment of the buffer zone as "appeasement", which it dubbed "a terrible idea".

[119] The Israeli Jerusalem Post newspaper described the establishment of the buffer zone due to Turkish threats as a "rewriting of international law", which implicitly recognized a "right to invade" and would have great implications for other world conflicts by allowing militarily powerful nations to unilaterally assert themselves over weaker ones.