Five weeks ago, when Germany's Foreign Ministry acknowledged a "rumble" in relations with Turkey, it was a diplomatic euphemism for a grave standoff.

Demands had been made on Germany to extradite followers of the US-based Turkish cleric Fethullah Gülen, and there were threats of pulling the plug on the controversial refugee swap with the European Union. And then German members of parliament were prevented from visiting Bundeswehr soldiers at Turkey's Incirlik Air Base. Each point came across as absurd to Germans, but the overall tone made it even worse.

Instead of discussing problems rationally, Turkey chose to escalate the standoff. Germany's ambassador was repeatedly summoned, which was consistently immediately communicated to the press. That is not how a good relationship works. German officials had to remind themselves that Turkey is actually a friend: a NATO member, an EU candidate and a trade partner.

Yes, Turkish officials felt misunderstood and unfairly treated. They were under the impression that Germans were less appalled by July's coup attempt than they were by President Recep Tayyip Erdogan's response to it. This impression may well have been accurate. Germany's foreign minister made a hypersensitive attempt to belatedly show some sympathy. Chancellor Angela Merkel also had to walk on eggshells after June's Bundestag resolution to recognize the century-old Ottoman slaughter of Armenians as genocide. From the perspective of Turkish officials, that was the greatest blow.

Germany was extremely lenient. Critics say the government has spinelessly caved in. But it was the price of accessing Incirlik, which not only has domestic significance, but is also important for NATO's fight against the "Islamic State," which requires the Bundeswehr's skills: Germany's parliament will only grant the mission new mandates if legislators can visit the army at the air base.

The lenience from Germany was essentially an offer to improve the tone of discussions, which is normal in partnerships. All accounts have been settled. Turkey must implement the refugee-swap agreement it negotiated with the EU in the spring and accept that visa-free travel is not without stipulations. The country should also listen to criticism with regard to violations of the rule of law, human rights and press freedom - especially when criticism comes from a trusted partner. Turkey must show that this can be done without a "rumble," for there is no reason to be offended.

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