NATO, a key element in Turkey’s security architecture for 65 years, is no longer seen as an indispensable ally for some in Ankara. Loud and sharp criticism toward the Alliance that had been a bulwark against Soviet expansion in Europe during Cold War is now a daily routine in Turkey.

Bullied and intimidated by the Soviet leadership in the aftermath of the World War II, acquisition of NATO protection and membership had been an urgent foreign policy goal for Turkey in the late 1940s when the organization was taking shape in its nascent days. Led by the U.S., NATO in 1952 extended its cover toward Turkey and Greece, two countries vulnerable to the menace of expanding Soviet communism in NATO’s southeastern flank.

Since then, NATO has been the paramount tenet of Turkey’s security framework in a region riven with sectarian strife, ethnic conflicts and lingering territorial disputes between nation-states. But no more.

Abandoning NATO was a marginal political position brought by fringe left groups or hardcore Islamists who have no relevance or strong representation in mainstream politics. Once disregarded as irrational, the idea of leaving NATO suddenly gained a new currency and this time among government figures with political influence over decision-making.

A senior lawmaker from ruling Justice and Development Party (AKP), Samil Tayyar, has recently called NATO a terrorist organization, which he claims “involved in dirty acts” to topple civilian governments in Turkey. For Mr. Tayyar, a former advisor to President Recep Tayyip Erdogan, NATO became a threat to Turkey and abets terrorist organizations across the region. He even went to portray NATO along with the Islamic State in the same category of terrorist groups, including Kurdistan Workers’ Party (PKK), and Fethullahist Terrorist Organization (FETO). Turkey considers PKK and FETO as terror groups.

In NATO’s new plan, President Erdogan even should not exist, Hurriyet daily quoted Mr. Tayyar as saying. His remarks do not only reflect marginal thoughts of a single disenchanted lawmaker angry about the lack of support lent to Turkey in its fight against its enemies. His statement illustrated a prevalent sense among senior government officials in Mr. Erdogan’s inner circle. For Turkish authorities, any form of criticism from the West toward anti-democratic practices, human rights violations under emergency rule in Turkey is tantamount to waging war against Turkey.

Turkey associates criticism from its allies with “betrayal” — ill-intentioned actions bent on sowing discord and internal instability in Turkey. This perceived threat took a firm hold in the government whose anti-NATO sentiment and discourse have only sharpened. Mr. Tayyar even called on Turkey to withdraw from NATO if the West, or the U.S. in particular, fails to meet Turkish demands.

And the partner that will replace NATO is Russia, long Turkey’s rival in the region. It was a threat by Russia’s predecessor, the Soviet Union, that NATO was formed and let Turkey join after the World War II.

Turkey’s cooperation with Russia over the Syrian conflict recently took a new form. Turkey now seeks to acquire Russia’s cutting-edge S-400 air defense system as part of its plan to have a coherent long-range air and anti-missile defense system, a long-sought project that have run into multiple delays in the past decade.

After rejecting Russian contender for its project three years ago over its high cost, Ankara seriously began to contemplate the acquisition of Russia’s system in a new preference that would put Turkey at loggerheads with its NATO allies. The subject first emerged during the bilateral meeting between Russian President Vladimir Putin and his Turkish counterpart in early October last year on the sidelines of a global energy summit in Istanbul.

Mr. Erdogan broached the subject of advance cooperation in defense industry between the two countries, which only one year ago came to the brink of open confrontation after Turkish F-16s shot down a Russian warplane over Turkey-Syria border.

A recent report by pro-government Yeni Safak daily notes that Turkish officials consider procurement of the Russia’s most advanced air defense system to meet its urgent needs as NATO’s second largest army lacks long-range anti-missile system in a turbulent region buffeted by a number of conflicts.

3 years ago Turkey finalized its international tender by choosing Chinese missile producer China Precision Machinery Import-Export Corp. (CPMIEC) over a price of $3.44-billion. The offer was the cheapest and contained some clauses that foresaw technology transfer in some form, a long-running demand by Ankara, which embarked on an ambitious program to give a boost to its local defense industry.

But the choice over Patriot system produced by U.S. companies Raytheon and Lockheed Martin, Russia’s S-300 system, and European Eurosam, maker of SAMP-T, sparked a row with NATO allies which expressed dismay and fury over the selection of a non-NATO system. Turkey’s Western allies long pressed for either choosing an American system or a European one, both are inter-operable with NATO systems, and objected to Ankara’s procurement of Chinese and Russian system on the ground that it may oppose a threat to NATO if both countries somehow get access to NATO systems in Turkey.

Ankara faced a dilemma upon selection of Chinese system after Brussels made it clear that the system will not be made inter-operable with NATO radar system deployed in Turkey. Facing tremendous pressure from its allies, Turkey, in 2015, finally canceled the tender won by Chinese CPMIEC.

Instead, Turkey assigned the project to two local defense firms, Roketsan and ASELSAN, but have made little progress to build the system. That pushed Turkish officials again to turn to European and American companies. Last October, Russian contender was back in the game after Erdogan’s invitation.

According to Yeni Safak report, Russia’s S-400 now appears as the favorite system for the Turkish authorities. The consideration of the acquisition of Russian missile system reflects more than procurement of a defense technology, rather it reveals a geopolitical shift in the Turkish foreign policy.

Recent Astana talks became an embodiment of new cordial relations between Turkey and Russia after they moved to mend ties strained by Turkey’s downing of a Russian warplane in late 2015. Last summer, Mr. Erdogan sent a letter of apology to Mr. Putin to end a dangerous row between the two countries. What started as a rapprochement in relations since then has evolved into a strategic realignment in not-too-subtle defiance of the Western-led international system.

Russia’s ironclad support for Mr. Erdogan’s government in the first moments of a coup attempt last summer paid off for Moscow as Ankara displayed irrevocable boldness and eagerness in abandoning decades-old strategic ties with NATO and the U.S., two core pillars of Turkey’s defense architecture since early days of the Cold War.

What pushed Turkey’s relations with the West to a breaking point in slow fashion was Mr. Erdogan’s relentless crackdown on opponents of all sorts in the aftermath of the coup. Turkey even went to purge its entire staff of representatives to NATO headquarters and command posts in Europe, nearly 400 military officials. The imprisonment of almost all pro-NATO commanders and generals within the Turkish military is another clear-cut indication of worsening relations and the Turkish government’s cold feelings about preserving ties with NATO.