"We take into account the sensitivities of our Turkish friends about the threats posed by foreign powers on the (Syrian) borders. The international community is aggravating the conditions in Syria. The United States is illegitimately feeding some organizations in Syria." Russian Foreign Minister Sergey Lavrov made these remarks during his critical visit to Turkey last week, during a joint press conference with Foreign Minister Mevlüt Çavuşoğlu. The subject was the YPG, the Syrian extension of the PKK terrorist organization.

These expressions become more meaningful when one recalls Lavrv's words to Çavuşoğlu some four years ago. Lavrov expressed his opinion to Çavuşoğlu that the YPG should participate in the Astana process as the "official interlocutor."

The same Lavrov gave signals to approach Ankara's theses the previous week, just before his visit to Turkey, as a result of all the critical developments that have passed since then, and the deepening of Turkish-Russian relations as a result. And he evaluated a possible Turkish operation against the YPG with the following words: "Russia has almost no military mission left in Syria. Of course, Turkey cannot remain indifferent to terrorism in northern Syria. The U.S. encourages separatism in the east of the Euphrates."

Many analysts considered Lavrov's words and other statements from Moscow as the green signal for the operation. So what has changed in four years? In order to understand this, it is necessary to go back not only to the past four years but also examine the chronology of the developments that resulted in the deepening of relations between Ankara and Moscow.

In November 2015, for the first time in decades, a NATO member country, Turkey, shot down a Russian warplane.

Russia was not aggressive, it was continuing that process with more passive-aggressive sanctions such as trade and tourism, when a coup attempt took place in Turkey. That was a turning point that transformed Turkish-Russian relations.

While the U.S. did not choose its side at first between the putschists and the legitimate government with the magic words "peace and stability," while it took two weeks for the European Union to send a representative, Russian President Vladimir Putin was one of the leaders who called President Recep Tayyip Erdoğan and conveyed his support.

One month after the coup, we started the first military operation in Syria. While the operation was going on, there was a first in Istanbul. The Russian ambassador was killed by a Daesh-looking Gülenist Terror Group (FETÖ) member in front of the cameras.

Both leaders read this unfortunate event as a way to sabotage their countries' relations. However, this is exactly why the relations between the two countries emerged from each crisis stronger. So much so that when the Russian plane was shot down, no one could have predicted that Turkish-Russian relations would progress to the extent of purchasing the S-400. As a matter of fact, it is a fact that the changing dynamics in Turkish-Russian relations, from the S-400s to the construction of the Akkuyu Nuclear Power Plant, from the liberation of Karabakh to our last operation in Syria, disturbed the Western power centers.

It is a fact that these groups will want to use the YPG issue, which remains an important snag in the relations between the two countries. For this reason, if an agreement can be reached with Russia on the YPG, it is possible that the doors of a new process will be opened.

At this point, let us remind you of our red line declared by President Erdoğan on June 26, 2015: "I am calling out to the whole world: We will never allow the establishment of a state in the north of Syria, in the south of Turkey, no matter what the cost."

Let us note with satisfaction the emphasis on both the fight against terrorism and separatism in this statement. However, let us remind you that the YPG still has an official office in Moscow, although the Russian authorities deny it. In the geopolitics that was reshaped after the Ukraine intervention, the Turkish-Russian relations need to move forward in a healthy way, on the "red lines," especially when all eyes are on Turkey and Russia on the grain corridor in Ukraine.

Moreover, Turkey holds the key to membership of Finland and Sweden, which want to become NATO members against the Russian threat. Putting all this together, it is possible to say that there is a critical YPG threshold in relations with Russia and this threshold must now be crossed.