Introduction Turkey, an integral member of the North Atlantic Treaty Organization (NATO), faces a number of political and economic challenges, including the turmoil following the thwarted coup attempt in July 2016, ongoing conflicts in Syria and Iraq, and increasingly complicated relationships with international partners. These challenges come in the midst of the June national elections called early by current President Recep Tayyip Erdoğan of the Justice and Development Party (AKP). Recently, Turkey has accelerated domestic defense developments and foreign defense partnerships, including by purchasing a Russian defense system. This article analyzes these defense decisions and their impacts on the structure of Turkey’s relationship with its fellow NATO allies. Turkey’s Defense Environment and NATO As a long-time NATO member and ally to several Middle East nations, Turkey plays a significant defense role in the alliance. The country hosts an X-band missile radar and has historically hosted Patriot missile batteries. Incirlik Air Base, in southeastern Turkey near Adana, is both a site of international military cooperation and a U.S. staging base for air missions in Syria and Iraq. Most recently, the 39th Air Base Wing at Incirlik has aided in the air campaign against the Islamic State of Iraq and the Levant (ISIL) from Turkey. Despite hosting military assets and remaining a member of NATO, domestic political factors have complicated Turkey’s foreign relationships. The actions taken following an unsuccessful coup attempt in July 2016 and a controversial constitutional referendum in April 2017 have led to allegations of increasing authoritarianism by the AKP. These concerns with the domestic situation have led to somewhat strained relationships with nations in Europe and beyond. In addition to NATO-operated systems, Turkey has developed domestic missiles and entered negotiations to buy foreign platforms. Turkey’s will to acquire new and upgraded missile systems likely stems from domestic security interests. There may be geopolitical undertones, especially guiding the decision to buy a system from Russia, but the foundational interest for the government is still national stability. The missile developments and international deals suggest Turkey is more aggressively pursuing a domestically sufficient defense industrial base. In early 2018, President Erdoğan indicated that he is interested in producing almost all defense products domestically except for in emergency situations. As a member of the Missile Technology Control Regime (MTCR), Turkey has unfettered trade access to thirty-five of the world’s most advanced missile producers. Last summer, Turkey tested their first domestically-constructed ballistic missile, the Bora, which has a range of approximately 280 kilometers and can carry payloads of up to 450 kilograms. It is produced by Roketsan, one of the largest Turkish defense firms. In April, Turkish government officials announced the development of another Bora missile, the Bora-2, which the minister of defense said will have a longer range. This has resulted in some concern because the MTCR limits the range of surface-to-surface missiles to a range of 300 kilometers. The Russian S-400 While the Bora missile is a surface-to-surface platform, Turkey has also been pursuing a long-range air defense system for some time. After failed talks with China and the United States, the Turkish government entered talks with Russia over the S-400 system. The S-400 is an air defense platform that uses mobile launch vehicles and has a range of 120 to 380 kilometers. After months of negotiations, Turkey and Russia have agreed to a $2.5 billion deal for four S-400 missile batteries. It makes Turkey the first NATO country to purchase the S-400, which has led to numerous statements of concern by U.S. and NATO officials, principally in two areas: the perception of relations and the compatibility of defense systems. For some analysts, the purchase symbolically represents Turkey defying NATO norms and cooperating with the nation NATO often works to contain. This is perhaps the driving force behind the disagreement: the signal that the purchase of the S-400 sends regarding the strength of the Turkey-NATO relationship. At a State Department briefing in September 2017, Spokesperson Heather Nauert said that the United States has concerns about the purchase. She indicated operability and symbolic concerns about nations working within the alliance on various issues. The second compatibility issue concerns whether the S-400 will be interoperable with other NATO equipment in the region. NATO in Europe has established a network of missile defense radars and interceptors. NATO’s stated goal is to provide “full coverage and protection” for European NATO states. A Pentagon spokesperson conveyed the operability concern with the S-400 this past summer. In March 2018, Secretary General of NATO Jens Stoltenberg said there had not been a request to integrate the systems and that integration “would be difficult.” The United States has not made a concrete decision of whether Turkey will face consequences for the purchase. However, 11 Democratic senators signed a letter indicating concerns about Russia’s S-400 negotiations with a number of nations, including Turkey. The letter questions whether the purchase would violate the 2017 Countering America’s Adversaries Through Sanctions Act (CAATA). Besides the sanctions concerns, a draft piece of legislation released by the U.S. House has a clause that would temporarily block some defense sales to Turkey, pending a review of the broader U.S.-Turkey relationship. Conclusion Barring major political changes, it is likely Turkey will acquire the S-400 air defense system from Russia and continue to commit resources to the development of a self-sufficient defense industrial base. These developments are part of an increasingly independent Turkish foreign policy, spearheaded by Erdoğan and the AKP. Turkey continues to contribute a relatively standard amount to NATO’s civil and military budgets. However, from a defense developments perspective, the Russian S-400 purchase signals more of a rocky diplomatic relationship between NATO and Turkey’s AKP. It is unlikely the S-400 will be integrated into the NATO missile defense architecture, which will lead to short-term difficulties among alliance members. It is also too early to tell what reaction, if any, the U.S. Congress will take in response to these defense developments. While there will be political tensions due to the S-400 deployment, Turkey remains a significant NATO ally due to its geographic proximity to the Middle East. In addition, one positive development is that Turkey is still open to further cooperation on missile defense with other NATO partners. Turkey’s state press reported that the government recently signed a ‘letter of intent’ with France and Italy on defense cooperation. This could include further missile defense cooperation with their Western European NATO neighbors. While there will be short-term tensions resulting from the S-400 purchase, it is highly unlikely Turkey will withdraw from the alliance or completely de-commit from NATO’s mutual defense goals in the long-term. Disclaimer Los Alamos National Laboratory strongly supports academic freedom and a researcher’s right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness.