For the last several weeks, Turkey blocked what NATO hoped would be a quick accession for Sweden and Finland – who applied for NATO membership for the first time despite their history of neutrality – much to the chagrin of its NATO allies. Turkey’s pause centers primarily on what Turkish President Recep Tayyip Erdogan sees as Swedish and Finnish sympathy for Kurdish militants, which Erdogan has deemed to be his country’s primary enemy. However, in a three-page memorandum signed by Finland, Sweden, and Turkey, the two Nordic countries agreed to withhold support for Kurdish fighters in Syria and followers of  Fethullah Gulen, a U.S.-based Turkish cleric blamed by Mr. Erdogan for fomenting a coup in 2016.

Despite their eventual agreement, the last few weeks have brought into question Turkey’s reliability as a NATO ally, though the debate did not start there as many NATO allies, including the United States, have grown increasingly vexed with Turkey over the last decade. Turkey, despite its key position in NATO, is a tricky ally.

From the Beginning

For decades, Turkey has proven challenging for its NATO allies after joining NATO in 1952 as a means to bolster Europe’s eastern flank against communism. Turkey is often perceived as a bit of an obstructionist, which is often problematic as decisions made by NATO allies require consensus across all members. For example, in 1974, the Muslim-majority country invaded Cyprus, leading to a conflict with Greece, a fellow NATO ally with whom Turkey has an antagonistic history.

The obstructionism spilled over into the twenty-first century. In 2009, Turkey held up the appointment of a NATO leader from Denmark, claiming the Danes were too tolerant of cartoons portraying the Prophet Muhammad and too sympathetic to Kurds based in Turkey, similar to its apprehension about Sweden joining the alliance. A few years later, Turkey deliberately delayed a NATO plan to reinforce Eastern European countries in the face of Russian aggression. Most recently, Turkey deployed ships near Greece to explore gas reserves, prompting France, another NATO ally, to send ships in support of Greece.

Turkey is a Key Part of the Alliance

Despite frustration among its allies, Turkey continues to play a key role in the alliance. As the Hill recently reported, most Biden administration officials and lawmakers agree that Turkey “provides a key bulwark of security for NATO in the Black Sea and has provided arms to Ukraine.” Further, for NATO, Turkey occupies a strategic position between Europe and Asia, which is particularly important given NATO’s updated strategy document that mentions China for the first time in its history and as the alliance expands its partnerships with other countries in the Indo-Pacific.  

For the United States, the relationship dates back decades. Turkey hosts the Incirlik Air Force Base where the Americans store approximately 50 nuclear weapons. As the alliance faces off against Russia after its invasion of Ukraine, Turkey, once again, shows its importance to the alliance as Turkey is in a unique position to broker potential peace talks to end the war. Despite Turkey’s important position within the alliance, several issues hinder Turkey’s relations with its NATO allies, particularly the United States.

The Kurds – Allies or Terrorists?

The United States and its NATO allies have been at odds with Turkey over the Kurds, a primarily Muslim ethnic group of about 30 million people with ambitions of autonomy that live in parts of Turkey, Iraq, Syria, and Iran. About half of the Kurds in the region live in Turkey, and many of them, including members of the Kurdistan Workers’ Party (PKK) – which Turkey considers to be a terrorist group – have resorted to violence and terrorism to achieve this aim.

In particular, Turkey is angered over America’s aid to a group of Kurds in northern Syria. In 2015, the United States turned to the Syrian Kurds for assistance in its fight against the Islamic State. The group, the Kurdish People’s Protection Units, or YPG, partnered with Arab groups under the Syrian Democratic Forces, or the SDF, to help the United States fight Islamic State. Turkey laments this pairing as Mr. Erdogan argues that the YPG is closely aligned with the PKK. American aid and cooperation with the YPG have angered Mr. Erdogan, seemingly becoming a point of contention in Turkey’s relationship with both the United States and NATO.

And Then There is Russia

Perhaps the biggest irritant in the United States and other NATO allies’ relationship with Turkey are the warming ties between Mr. Erdogan and Russian President Vladimir Putin. As the United States and NATO straddle the line between fully engaging and pacifying Russia over its war in Ukraine, Russia remains one of NATO’s key security challenges, thus complicating the situation should Turkey’s relationship with Russia continue to deepen.

Specifically, the United States and its NATO allies express concern over Turkey’s purchase of the Russian S-400 weapons system in 2019. NATO allies grew concerned that Russia might gain access to the U.S.-led F-35 program, a highly coveted fighter jet that United States has enthusiastically sold to its allies. As a result, the United States suspended Turkey’s participation in the F-35 program as the Pentagon argued that an ally could not participate in the program while also purchasing a missile defense system from an adversary.

After being expelled from the F-35 program, Turkey has been cajoling the United States to sell it F-16 fighter jets instead. Now, the Biden administration seems open to such a sale after Turkey dropped its opposition to NATO expansion into the Nordic region. This has been met with resistance by many members of Congress, including Senate Foreign Relations Chairman Robert Menendez, who has warned the Biden administration against entertaining such Turkish requests for more F-16 fighter jets. The United States risks rewarding behavior unbecoming of a NATO ally should the Biden administration agree to sell the F-16 jets to Turkey, however.

The Challenges Still Remain

Turkey remains an important member of the NATO alliance. Yet, its NATO allies are continually frustrated over Mr. Erdogan’s willingness to hold up alliance progress over the Kurds and Turkey’s growing relationship with Mr. Putin. Mr. Erdogan backed off on holding up Sweden and Finland’s accession into NATO, and the Biden administration and other NATO leaders are more open to offering Turkey what it wants – whether support over the Kurds or sales of F-16 fighter jets. The NATO allies, however, must take care not to acquiesce too much in Mr. Erdogan’s favor as the challenges in the NATO-Turkey relationship still remain.