Turkish President Recep Tayyip Erdogan has become a thorn in the side of many European leaders. His authoritarian politics, bombastic statements, and arrests of German citizens have injected particular tension into German-Turkish relations. Hopes for improved ties following the March 2016 E.U.-Turkey migration deal have been displaced by a diplomatic showdown that sees two powerful NATO allies locking horns — familiar ground for Erdogan, but almost unprecedented for post-war Germany.

Senior Turkish officials suggest the downward spiral is driven by German politics and express confidence that ties with Berlin will improve after the Sept. 24 election. But anyone in Ankara who thinks this is whistling past the graveyard: German Chancellor Angela Merkel herself has stated that Turkey should not become an E.U. member and separately warned that Germany will scale back its extensive economic ties with Turkey. This clash is likely to persist — and bring collateral damage for the broader European-Turkish relationship — well beyond election day.

Downward Spiral

The timeline below charts the major diplomatic incidents between the two nations over last 18 months, revealing a near-constant barrage of back-and-forth volleys ranging in severity from ambassadorial reprimands to military redeployments.

Erdogan’s latest salvo came on Sept. 9 with a warning to Turkish citizens not to travel to Germany, mirroring Germany’s guidance to its citizens after a spate of detentions in Turkey. Earlier, on Aug. 18, Erdogan described Germany’s Christian Democratic, Social Democratic, and Green parties as “enemies of Turkey” and encouraged German voters of Turkish descent, who number about 1.2 million (out of a total electorate of 61.5 million), to vote against them in the upcoming election. Merkel and Foreign Minister Sigmar Gabriel responded with justifiable indignation, though this is hardly the only provocative statement Erdogan has directed at Germany in recent months.

In March, ahead of Turkey’s constitutional referendum on the expansion of presidential powers, Erdogan accused Merkel of using “Nazi methods” to suppress free speech after local German authorities barred some pro-referendum rallies at which senior Turkish politicians planned to speak. This was an offensive accusation for obvious reasons and struck at the heart of Germany’s post-war self-image as a country that has, as its greatest achievement, unequivocally renounced anti-democratic methods.

Germany was not the only country to block such rallies. Similar actions in the Netherlands and Austria also drew Erdogan’s ire. His vocal outrage may have been, in part, a tactical calculation. He likely sought to draw support in the referendum from the Turkish diaspora in Europe by presenting himself as an aggrieved defender of Turkish sovereignty and national pride. For their part, these European governments were able to leverage the moment to issue warnings to Erdogan against instrumentalizing Turkish populations in Europe and to capitalize on growing anti-Erdogan sentiment in their countries — a bizarre sort of win-win scenario.

The security realm has not been spared these recriminations. Turkey has, on three occasions, blocked German parliamentarians — who voted in June 2016 to support a resolution recognizing the Armenian genocide — from visiting German troops stationed at the Incirlik and Konya military bases in Turkey. Ankara has also launched legal battles against offending German comedians and accused German companies operating inside Turkey of supporting terrorism (a claim it later withdrew). With the arrests of two more German citizens on Sept. 1, the number of Germans currently being detained in Turkey has risen to over 50, 12 of whom German authorities say are held on political charges (including journalists and human rights experts).

In response, Germany has taken increasingly tough steps toward Turkey. In May, German authorities ignored Turkish extradition requests and granted the asylum claims of some Turkish military officers and officials who feared for their safety following Erdogan’s post-coup purge. According to media reports, 615 former Turkish officials and dependents have sought asylum in Germany. Some cases yet to be adjudicated include two officers Turkey accuses of direct participation in the coup attempt, which will guarantee continued bilateral friction on this issue.

Berlin has also moved its 260 Incirlik-based troops involved in the counter-ISIL mission to Jordan, one of the boldest steps to date. It issued a travel warning advising German citizens about the risks of travel to Turkey, and warned Ankara that it would refuse to allow balloting in Germany (among Turkish citizens) if Erdogan decides to hold a referendum in Turkey on reinstating the death penalty.

Most recently, in a televised election debate on Sept. 3, Merkel and her SPD rival for the chancellorship, Martin Schulz, sought to outdo each other in criticizing Turkey’s direction. They disagreed only about means: Schulz called for ending Turkey’s accession talks with the European Union, and while Merkel demurred, she stated unequivocally that Turkey “should not become a member of the EU” and that she had always opposed accession. Condemnation of Erdogan turned out to be one of the central points of agreement in the election debate.

Motivations

For a country that instinctively stresses dialogue and diplomacy — and particularly for a leader like Merkel, who embodies rational pragmatism — Germany’s stance is striking. It is hard to recall such sustained acrimony levied publicly by Germany toward another country in the post-war period, let alone toward a treaty ally.

The current standoff reflects a dramatic change from March 2016, when Merkel brokered the E.U. deal with Ankara to halt the flow of migrants and asylum-seekers from Turkey to Greece. The price tag on the deal — €6 billion in aid, visa-free travel for Turkish citizens, and intensified accession talks — seemed to attest to Europe’s weak negotiating position. Eighteen months later, Germany’s increased willingness to respond in kind to Erdogan’s rebukes stands in stark relief. It may be partially explained by the closure of the migrant land route through the Western Balkans, which has made Germany less vulnerable to migration pressures from Turkey.

It also has to do with politics in both countries. Public opinion in Germany has turned decidedly against Erdogan and his government: A survey earlier this year indicated that an overwhelming majority of German voters, regardless of party inclination, supported a tougher line toward Turkey. There is virtually no electoral constituency of any consequence supporting closer relations. Deepening authoritarianism in Turkey has only reinforced that position across the political spectrum.

In Turkish politics, Erdogan benefits in the short term with his conservative and nationalist base by defying Europe’s acknowledged leader — a leader that, in the eyes of some Turks, stands unfairly between their nation and visa-free travel to the European Union, a full customs union, and, ultimately, membership in the union. By channeling Turkey’s national sense of indignation over Europe’s repeated rebuffs in Merkel’s direction, Erdogan is able to rally his base while distracting from economic difficulties in Turkey and from domestic opposition toward his own policies.

Erdogan also harbors resentment over what he perceives as an inadequate show of support following the attempted coup in July 2016. He feels betrayed by Germany’s criticism of the steps he considers justified and necessary to sustain democratic rule. There is also deep suspicion and paranoia in Turkey about supporters of exiled Turkish spiritual leader Fethullah Gulen, whom Erdogan blames for the coup attempt. Erdogan alleges that Germany (along with many other nations) harbors Gulenists who represent a threat to the Turkish state.

Implications

There are several aspects of the German-Turkish relationship that have been or could be affected by the current row. Economically, Germany is Turkey’s biggest trading partner, with trade totaling $34.4 billion in 2015. Germany is the largest export market for Turkish products by a broad margin and the second largest import market after China. There are nearly 6,400 German companies operating in Turkey. German tourism totaled 5.5 million last year alone, the most from any nation and 15 percent of all tourism in Turkey. Germany knows it holds the upper hand: Berlin will not want to damage German business interests in Turkey, but Merkel and her government will not be coerced by threats against German firms. Economic interests may therefore be one of the few checks on how far Erdogan is willing to push Berlin.

Ripple effects will surely be felt inside NATO, however, where consensus and unity are required for decision-making. So far, significant impacts have been avoided, if only barely. After asking for and receiving NATO air and missile defense reinforcements — which included German PATRIOT systems — from 2013 to 2015, Turkey now has signed a $2.5 billion deal with Moscow to procure four S-400 air defense batteries over other U.S.- and European-made systems. Unlike the United States, Germany has bitten its tongue publicly despite the dangers to NATO interoperability and solidarity vis-à-vis Russia. Because German industry does not have a direct commercial interest in the S-400 sale, it may decide to let the United States take the lead in managing this disagreement. Given Germany’s economic leverage with Turkey, however, the question of whether it should take a pass on this issue is a valid one.

In a more public clash, NATO Secretary General Jens Stoltenberg had to step in to mediate when Turkey again riled members of the German Bundestag. The incident originated with Erdogan’s decision to postpone a German delegation visit to the NATO forward operating base at Konya, where approximately 30 German troops are stationed in support of the alliance’s AWACS air surveillance contribution to the counter-ISIL coalition. Stoltenberg persuaded Ankara to allow the visit on the condition that it occur under NATO sponsorship, averting a showdown that could have jeopardized the mission itself.

That the Germans are still supporting NATO’s efforts in Konya after pulling their nationally-flagged troops from Incirlik shows that, at least for now, Berlin is willing to separate its NATO commitments from its bilateral political disagreements. In the near term, Germany is unlikely to block future NATO assistance measures requested by Turkey from going forward. It may, however, be less willing to answer the call with contributions of its own going forward, especially for deployments that require a Bundestag mandate — as the current AWACS deployment (and past missile defense support) did.

Germany’s bilateral defense relationship with Turkey may suffer, too. Berlin has already announced that it will exercise stronger control over arms exports to Ankara, a relationship worth $99 million in 2016. Opposition parties in the Bundestag have called for a complete halt to arms sales, which Merkel’s government thus far has resisted, although 11 cases reportedly have been denied since the start of 2016.

As for the European Union, the most significant impact of frayed relations will be to the overall trajectory on Turkey’s accession. Post-election, it is unlikely that any new governing coalition in Germany would favor Turkish E.U. membership, but it is possible Berlin might preserve a modicum of ambiguity by declining to seek a consensus to break off the process. Neither side wants to assume blame for ending the talks altogether, and Germany as well as other European states have a direct interest in intelligence-sharing with Turkey and the broader fight against terrorism. Regardless, the promises made by Merkel and Schulz in the election campaign ensure that the European Union will assess its relationship with Turkey at the October E.U. Council meeting. Ankara seems resigned to the reality of its prospects, or at least content to use an eventual rejection for domestic political gain.

Expectations

While the temperature might decrease a bit after the Sept. 24 German election, the relationship will not be repaired anytime soon. This is because the core of the issue will not disappear: Turkey’s shift toward authoritarianism, and how NATO and the European Union deal with allies and partners who are diverging not just diplomatically but also in their foundational values.

The new assertiveness in German policy toward Turkey cannot be separated entirely from the rise of President Trump and the weakening of U.S.-German ties. If Berlin loses confidence in Washington’s ability to manage the overall western relationship with Ankara, then it may feel the need to strike a more independent course. Growing German responsibility inside the western democratic coalition will involve further growing pains and challenges, which the next Chancellor will have to confront and reconcile with Berlin’s top foreign policy priorities.

Lisa Sawyer Samp is a Senior Fellow in CSIS’s International Security Program, and formerly the Director for NATO and European Strategic Affairs at the National Security Council. Jeffrey Rathke is a Senior Fellow and Deputy Director of CSIS’s Europe program, and formally a NATO official and a Foreign Service Officer at the State Department.