On August 19, the Turkish authorities reported that the Syrian Air Force had attacked a convoy of Turkish soldiers, which was directed to border checkpoint No. 9, in Idlib province.
On August 23, during a phone call, Russian president Vladimir Putin and Turkish President Recep Tayyip Erdogan discussed various aspects of Russian-Turkish cooperation in the context of stabilizing the Idlib de-escalation zone. According to the Kremlin website, the two leaders agreed to intensify joint efforts to eliminate the terrorist threat emanating from that region and ensure the implementation of the Sochi Memorandum of September 17, 2018.On the same day, it was announced that Erdogan will pay a one-day-visit to Russia on August 27.
Commenting on Erdogan's visit, Russian analyst Boris Dolgov, a senior researcher in the Institute of Oriental Studies of the Russian Academy of Science, said:“The mere fact that Turkish president is coming to Russia in such a hurry shows that Turkey does not want a confrontation at the moment, moreover Turkey can't get into direct confrontation with the Syrian forces." Dolgov recommended a firm stance towards Turkey, which he accused of playing a delaying game and trying to capitalize on differences between Russia and the US. 
The senior Turkish diplomatic correspondent Sedat Ergin wrote an op-ed in the Turkish newspaper Hurriyet that the attack on the Turkish convoy by the Syrian army, although Russia was notified about the convoy in advance, makes the situation "quite serious in all respects." It is worth noting that the wording of the Turkish Defense Ministry's August 19 statement attributed responsibility for the incident to Russia.
According to Ergin, the security crisis between Turkey and Russia should be seen as the de facto termination of the Sochi Agreement. Ergin opined that Russia's support for the Syrian army's military operations that commenced in May, and the very fact that Russian air forces participated in the operations, "clearly" shows that article 2 of the Sochi agreement is not being implemented. Article 2 states that Russia will "take all precautions to avoid military operations and attacks in Idlib." This article also asserts that "the current status quo in Idlib will be protected."
Below is Ergin's article:
The Fact That The Turkish Convoy Was Attacked, Despite Russia Being Notified In Advance About The Convoy, Makes The Situation Serious In All Respects
"Turkey and Russia have indirectly been at odds amid developments in Idlib in Syria's northwest. This was happening in contradiction to the great rapprochement in Turkish-Russian relations thanks to the arrival of the S-400 air missile systems.
"The alarming situation in the field has now been taken into a new verge with the air attack launched towards an on-the-go military convoy of the Turkish Armed Forces on Aug. 19 in Idlib.
"The Aug. 19 incident is a first in the sense that it was the first time a Turkish convoy has been subjected to an aerial attack in Idlib.
"Turkey's many military bases in the region have been subjected to attacks as Bashar al-Assad launched a systematic military campaign towards radical groups in Idlib last May, with the overt support of Russia.
"The previous ones, however, were artillery attacks. For instance, on June 27, the Syrian army launched an artillery attack on Turkey's 10th observation post in the southern rural Zawiya region in Idlib. In the attack, a soldier was killed and three soldiers were injured.
"These actions of the Assad regime have been putting Turkish-Russian relations on a stress test at every turn. Because after every incident, Turkey has been demanding Russia to keep its ally Syria at restraint, yet, these attempts have been doing no good to the attitudes on the field. Seemingly, Moscow, which has the influence to easily affect the regime - if it wants to - has been setting Damascus hands' free. This situation, taking place under the shadow of the warm climate of the S-400s, was becoming a source of trust problem, which was not openly revealed.
A very similar one to this problem was repeated on Aug. 19, on the field, on a very dangerous verge.
"The fact that the Turkish convoy was attacked, despite Russia being told in advance about the convoy, makes the situation quite serious in all respects. It is worth noting that the Turkish Defense Ministry's statement on Aug. 19 used a rhetoric attributing the incident's responsibility to Russia.
"In fact, the security crisis here should be seen as a result of the de facto termination of the Sochi Agreement, signed between President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin on Sept. 17, 2018.
"Article 1 of the agreement stipulates that 'Turkey's observation points will be fortified and continue its activities.' Today, the observation points are under attack.
"According to article 2, Russia will 'take all precautions to avoid military operations and attacks in Idlib.' This article also asserts that 'the current status quo in Idlib will be protected.'
"According to article 3 of the same agreement, 'a 15 to 20-kilometer-deep demilitarized zone in Idlib' was supposed to be established. Articles 5 and 6 of the agreement oversaw the 'removal of all radical groups, as well as tanks and cannons, within October 2018 in this region.'
It Is Inevitable That The Rapprochement Process Of Turkey And Russia Would Be Overshadowed
"In practice, Russia's support for the Syrian army's military operations that commenced in May, and the fact that Russian air forces ipso facto participation in the war, clearly shows that article 2 of the agreement is not being implemented. Russia, on the other hand, was voicing complaints from its own perspective about the implementation of the agreement, saying radical groups are not leaving the demilitarized zone and attacking the Russian military base in Khmeimim.
"With the ongoing reciprocal criticisms, Russia has put its weight in favor of the regime capturing Idlib, therefore, in favor of changing the status quo. After that, groups affiliated with the Free Syrian Army, which Turkey supports, entered the stage in Idlib, in a more distinguishable way, after May. This alteration bore the message that Ankara would not accept the change of the status quo in Idlib.
"This tension, which has been accumulating for some time, has morphed into a critical stage in the last week, when the regime entered the range of seizing Khan Sheikhun, in the south of Idlib. It is critical, because Turkey's ninth observation post is situated in Morek, about 10 kilometers south of Khan Sheikhun. As the regime captures Khan Sheikhun, it will create a situation such that this observation point will be surrounded by regime forces, from all sides, and land route with Turkey will be cut off.
"Since the observation posts were established within the framework of an agreement signed with Russia during the Astana process, the continuation of their presence is under Russia's guarantee. As a matter of fact, Russia also has observation posts, across the other side of the border.
"We can say that a sensitive, critical diplomatic process between Turkey and Russia awaits with the incident of Aug. 19. It should not be surprising if this comes up on the agenda of the close dialogue between Erdogan and Putin, in the forthcoming days.
"Taking this crisis under control is also important with regards to the fate of the trilateral summit in Turkey, between Erdogan, Putin and the participation of Iranian President Hassan Rouhani mid-September.
"It is inevitable that the rapprochement process of Turkey and Russia would be overshadowed, if the said situation fails to be taken under control and besetting outcomes come up in Idlib, like the Aug. 19 incident.
"It is obvious that a route full of high risks that needs to be managed really carefully is being followed in Idlib."