Coup-proofing? Making Sense of Turkey’s S-400 Decision

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On July 12, Turkey received the first elements of the S-400, a fourth-generation surface-to-air Russian missile system. Few recent weapon sales have been as geopolitically charged as this one. U.S. officials have threatened both military and economic sanctions should Turkey acquire the Russian system.

The delivery comes after many years of negotiations for more advanced air defenses. President Recep Tayyip Erdogan first discussed with Russia in August 2016 what would ultimately become a $2.5 billion agreement to procure four S-400 batteries, but Turkey has been pursuing air and missile defenses for over a decade. The S-400 announcement follows several previous tenders in which Turkey considered but ultimately did not buy the U.S. Patriot, the Chinese HQ-9, and the French SAMP/T. The arrival of the S-400 follows significant political turmoil in Turkey, most notably the shootdown of a Russian jet in 2015, the failed coup attempt of July 15, 2016—exactly three years ago today—and a new strategic partnership between Erdogan and President Vladimir Putin.

Stated U.S. concerns about the deal have primarily centered on the threat to the advanced F-35 tactical aircraft Turkey was slated to acquire. Most of the time, the F-35 flies with an exaggerated radar signature so that anyone observing it will not see its true signature. Turkish operation of the two systems together—and more specifically, when it is in stealth mode—would allow the S-400 to acquire intimate knowledge of the F-35’s radar signature. Such insights would almost immediately find its way back to Russia, and the capability of F-35s around the world could thereby be degraded. The location of the Russian sensors on the territory of a North Atlantic Treaty Organization (NATO) ally also provides a more forward-based position from which to observe other NATO aircraft and military exercises.

Analysts have struggled to explain Turkey’s air defense actions. Western officials and analysts alike have gone, as it were, through four of the five stages of grief: denial that Turkey would go through with a seemingly inexplicable decision, anger at the repercussions for the NATO alliance and threats to withdraw F-35 participation, bargaining with renewed offers for the Patriot, and now depression over the forthcoming deployment.

Getting to the acceptance stage requires an appreciation of Turkey’s foreign and domestic political calculations, above all Erdogan’s desire for survival. Analysts have been scratching their heads as to the U.S. failure to dissuade Erdogan, but Occam’s razor may be helpful here. Erdogan may want the S-400 for the exact reason the United States does not want Turkey to have it: precisely because it is built to shoot down the American-made aircraft currently operated by the Turkish Air Force. Both political and military aspects of the S-400 decision make sense inasmuch as Erdogan’s top priority is his own political survival.

Figure 1: S-400 Components Arriving in Turkey

Turkey’s Air Defense Timeline

  • January 2013-present: Rotational Patriot deployments in Turkey by other NATO members.
  • September 26, 2013: Turkey selects Chinese air defense offer, later cancelled on November 18.
  • November 24, 2015: Shootdown of Russian aircraft over Turkish airspace.
  • July 15-16, 2016: Coup attempt.
  • August 9, 2016: Erdogan-Putin summit, announcement of a new strategic partnership and interest in the S-400.
  • December 29, 2017: Turkey signs deal with Russia to purchase S-400.
  • July 12, 2019: S-400 delivery commences.

A New Strategic Relationship with Russia

Relations between Turkey and Russia have changed dramatically over the past few years. In November 2015, following Turkey’s downing of a Russian Sukhoi Su-24M, the two countries seemed on the brink of hostilities. They have since taken several measures to significantly increase political and military cooperation. Combined with distrust of the United States after the 2016 coup attempt by the Turkish military, the purchase and operation of S-400 units in Turkey may represent a form of tribute in the new Turkish-Russian relationship, part of Putin’s asking price for mending fences with Russia and support for Erdogan’s remaining in power.

Public analysis of Turkey’s consideration of the S-400 has largely consisted of seemingly objective, side-by-side comparisons of the Patriot system and the S-400 on the basis of characteristics like relative missile engagement range and radar coverage, and Turkey’s (ostensible) claim about technology transfer—as if this was just another weapons acquisition program.

On these grounds, it may seem odd that Turkey would diverge from its NATO allies. Unlike the S-400, the Patriot has a combat-proven record and scores of engagements in several conflicts. SwedenRomania, and Poland have in the last year announced plans to acquire the Patriot as a hedge against Russian aggression in Europe. Although it currently lacks omnidirectional radar coverage, such capability is coming for the future Patriot force. The Patriot has seemingly been good enough for Turkey since 2013, having been generously deployed for the defense of Turkish soil by NATO allies Germany, Netherlands, Spain, and the United States. At a June press conference in Japan, President Donald Trump seemed to sympathize with Erdogan, stating that Turkey was “not allowed” to buy the Patriot under the Obama administration, and he cast doubt on whether the United States would impose sanctions over the S-400. In fact, the Patriot has been offered to Turkey on numerous occasions, including in the 2013 tender during which Turkey eventually selected a Chinese system derived from the Russian S-300.

And as for Turkey’s stated objections relating to technology transfer, there has been no confirmation that Russia is giving Turkey any more of the sophisticated seeker and guidance technology than what the United States gives to other allied operators of the Patriot.

Such an approach largely misses the point. Turkey’s motivations might be better explained by two closely connected factors: possible internal threats to the Erdogan government and international relations with Russia. Turkey’s perspective on Russia and the United States is quite different from that of many other NATO members. The alliance as a whole has called out Russian aggression and begun to orient air defenses to the east. If internal and external political factors are taking precedence, sterile side-by-side comparison of S-400 and Patriot metrics may therefore be misleading.

Figure 2: Putin and Erdogan in February 2019


Although Turkey claims that its own personnel will man the S-400s, various Russian advisors and technicians will likely remain on the ground for training and maintenance, if not also for operational support. The presence of these advisors accompanying the hardware would also be tangible evidence of ongoing Russian support for Turkey. As with the Russian deployment of S-300 and S-400 batteries in Syria to protect Bashar al-Assad, the presence of Russian personnel and hardware is a strong signal of Russian support.

Besides political and economic benefits, Turkey may also want the S-400 for unique military reasons, namely the capability to shoot down aircraft operated by the Turkish Air Force.

A Capability to Shoot Down Its Own Planes

During the Turkish military’s attempted coup in July 2016, Turkish F-16 pilots bombed the Turkish Parliament and threatened Erdogan’s own plane. In the months that followed, Erdogan tried to “coup-proof” the country through mass arrests and by reportedly purging some 2,600 military officers, including half of Turkey’s fighter pilots.

Acquiring the S-400 may, in short, be part of Erdogan’s hedge against another coup, both by deepening his strategic relationship with Russia and by acquiring specific air defenses meant to combat another attempt to overthrow him.

Acquisition of the Patriot system would not fit in with Erdogan’s developing partnership with Russia. Nor would it suffice as coup insurance, since it is not tailored to shoot down Western aircraft. Having accused the United States of being behind the 2016 coup, Erdogan may be distrustful of U.S. air defenses to protect him in the future. Whether he is better off staking his survival on the Russians remains to be seen.

Next Steps

Now that Turkey has acquired the S-400, the question is what the United States will do in response. The United States appears to be prudently terminating Turkey’s involvement in the F-35 program. Like his predecessor Patrick Shanahan, acting Secretary of Defense Mark Esper has confirmed that the United States will suspend F-35 sales should Turkey acquire the S-400. Turkish pilots that had been training on the F-35 are being sent home, and a new foreign partner is being sought to substitute for Turkish involvement and investment.

Sanctions on Turkey for purchasing Russian military equipment are also likely. Following the Russian invasion of Ukraine, Congress in 2017 passed the Countering America’s Adversaries Through Sanctions Act (CAATSA), which imposes sanctions on any country purchasing significant military equipment from Russia. Turkey’s S-400 purchase puts the Trump administration in the awkward position of either enforcing sanctions on a NATO ally or pretending that Turkey’s S-400 acquisition is somehow a vital national security interest of the United States such that sanctions could be waived. Whether or not CAATSA sanctions are implemented, or for how long, allowing Turkey to have the F-35 is incompatible with Turkey’s operation of the S-400, and that sale must be terminated if Turkey operates the S-400.

But if Erdogan’s S-400 decision is driven by fundamental desire to preserve his rule—as a matter, as he says, of “national sovereignty”—then both the loss of the F-35 and CAATSA sanctions may be a price he is willing to pay.

If Turkey’s S-400 is indeed intended to provide military and political insurance for Erdogan against another coup attempt, it would go a long way to explaining why he is willing to endure considerable U.S. and NATO pressure to acquire it. This more specific purpose might explain why Turkish defense minister Hulusi Akar still maintains that Turkey remains open to acquiring the Patriot—as defense against other external threats. In the long term, Turkey may reverse the current move towards Russia, perhaps in a post-Erdogan period. If so, the prospects of both F-35 and Patriot air defenses could be reopened along with a future integration with NATO air defenses. For now, however, Turkey’s decision to acquire the S-400 represents a significant win for Russia.

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Tom Karako, "Coup-proofing? Making Sense of Turkey’s S-400 Decision," Missile Threat, Center for Strategic and International Studies, July 15, 2019, last modified April 27, 2021,