Tuesday’s NATO summit in London marks 70 years of the world’s longest and most successful military alliance. However, behind the smiles and handshakes, there will be serious concerns about NATO’s future. U.S. President Donald Trump has NATO in his sights, recently moving to substantially cut its contribution to the NATO budget; France’s President Emmanuel Macron recently declared that NATO is becoming "brain-dead."

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However, NATO’s biggest internal challenge remains Turkey.

Last week, Turkey tested its newly-acquired Russian S400 missile defense system against F16 fighter jets, despite S400s being incompatible with NATO hardware. Ankara is also threatening to veto NATO’s plans for the defense of Poland and the Baltics unless NATO backs Ankara's operations in Syria against the Kurdish People’s Protection Units (YPG).

Although the YPG contributed to the territorial defeat of ISIS, Ankara deems it indistinguishable from the Kurdistan Workers Party (PKK), which has been waging a separatist war against the Turkish state since the 1980s.

During the Cold War, Turkey was a bulwark against Soviet expansion. Its western orientation, large military and geostrategic location made Turkey a strategic asset.

Open gallery view A Turkish flag flies next to NATO logo at the Alliance headquarters in Brussels, Belgium, November 26, 2019 Credit: Francois Lenoir/ REUTERS

Today, however, the main security concerns of NATO are Russian belligerency, the spread of weapons of mass destruction, the deteriorating security situation in the Middle East and the associated threats of migration and terrorism. If anything, Turkey has contributed to the proliferation of these security threats.

Turkey has cosied up to Russia in many fields, but especially by purchasing its weapons. Ankara turned a blind eye to jihadists entering Syria through Turkey between 2013 and 2014, which contributed to the rise of ISIS. Turkey then created additional instability by twice intervening in Syria between 2016 and 2018. Last October, Ankara sent its forces together with its Syrian Jihadist proxies to crush the YPG.

Despite there being a Russian-brokered agreement in place, Turkey still wants to resettle Arab Syrian refugees in Kurdish areas, a policy which could lead to ethnic cleansing. Although Turkey hosts over 3.6 million Syrian refugees, Ankara threatens to "open the gates" for their migration to Europe unless more support is forthcoming for Turkey’s designs in Syria.

Meanwhile, through a state-owned bank Turkey violated the U.S. Iran Sanctions Act, ahead of the signing of the 2015 Joint Comprehensive Plan of Action (JCPOA), undermining attempts to prevent the proliferation of nuclear weapons.

If that were not enough, last September, Turkey’s firebrand President Recep Tayyip Erdogan declared that it was unacceptable that Turkey could not have nuclear weapons of its own.

Open gallery view Smoke billows from targets in Ras al-Ayn, Syria, caused by bombardment by Turkish forces, Wednesday, Oct. 16, 2019 Credit: Cavit Ozgul,AP

With Turkey appearing more of a hindrance to NATO than an asset, it begs the question what can be done? There is no mechanism or precedent for expelling a NATO member.

One possibility is to try to amend the North Atlantic Treaty to allow for the sanctioning or expulsion of a member state. However, this is unlikely to succeed: it would need unanimous support - and Turkey could just veto it. Other NATO members might also resist out of concern that they may one day be sanctioned.

Alternatively, NATO might want to bide its time. Perhaps Erdogan might lose the next election. Meanwhile, some kind of quid pro quo could be worked out. Ankara might support NATO’s defense plan for Poland and the Baltics in exchange for a limited backing of Turkey’s operations in Syria.

However, Turkey's presidential elections are not scheduled until another four years, and it is premature to conclude that Erdogan will lose. Despite the economic downturn, he remains highly popular, and still holds all of the country’s levers of power. Plus, transactional arrangements run counter to the spirit of the alliance, and Turkey’s activities in Syria is not something NATO should seriously entertain supporting.

The best option for NATO is to show Ankara tough love. Without NATO, Turkey is weak, especially after years of purges within its armed forces. Currently, Turkey has more fighter jets than capable pilots, and with over half of its high-ranking officers having been arrested or forced to retire, Turkey has lost a wealth of knowledge, experience and expertise.

Articles 4 and 5 of the North Atlantic Treaty offer Turkey an unprecedented security umbrella. Article 4 calls for member states to "consult" with each other whenever their territory or security is threatened, and Article 5 states that an attack against one is an attack against all.

Open gallery view Military officials by a Russian transport aircraft, carrying parts of the S-400 air defense systems, after it landed at Murted military airport outside Ankara, Turkey. Aug. 27, 2019 Credit: ,AP

But NATO’s support for Turkey goes beyond the call of duty. From Turkey'suse of military equipment produced by NATO members, to the deployment of Spain’s Patriot air defense system and the presence of NATO bases in Anatolia, Turkey’s security is all but guaranteed.

It is also through NATO that Turkish officers receive training and exchanges of views with some of the world’s most sophisticated militaries, as well intelligence-sharing and the opportunity to participate in NATO missions.

Turkey should be informed that continued intransigence could lead to NATO and its member-states to provide only baseline cooperation.

It should also be explained that anything beyond the most limited support could become contingent on Ankara upholding other articles of the North Atlantic Treaty, such as Article 1, which stipulates that before NATO members resort to force they should first seek "peaceful means in such a manner that international peace and security and justice are not endangered," and Article 2, which calls for members to strengthen "their free institutions" by "promoting conditions of stability and well-being."

Turkey needs to be reminded of the benefits of its NATO membership and the consequences of losing goodwill. It is in Ankara’s interests to seek common cause with the world’s most successful military alliance - or else Turkey risks becoming just another satellite of an ever-assertive Russia.

Dr Simon A. Waldman is an associate fellow at the Henry Jackson Society and a visiting research fellow at King's College London. He is the co-author of "The New Turkey and Its Discontents" (Oxford University Press, 2017). Twitter: @simonwaldman1