The release on Friday of American pastor Andrew Brunson is a vindication of President Trump's hard-edged negotiating strategy toward Turkey. Although technically a Turkish court authorized the release, it is the result of direction from Turkish President Recep Tayyip Erdogan government.

Trump had consistently ratcheted up the pressure on Erdogan's government while rightly refusing to extradite Fethullah Gulen, a Turkish citizen whom Erdogan accuses of plotting coups against him. The evidence against Gulen is nonexistent, demonstrating that the charge is spurious and politically motivated.

Many had doubted that Trump's pressure-centric strategy would ever pay dividends against Erdogan. They believed that Trump was more likely to end up seeing Brunson suffer a longer and harsher imprisonment. The context for these concerns was not unfounded – after all, Erdogan's mental stability and penchant for theatrical escalations are longstanding issues – but Trump won this arm-wrestling match by focusing on the numbers.

Turkey's continuing economic troubles were an excellent pressure-point. The sanctions that Trump imposed on Turkey in relation to Brunson's detention come in the context of that nation's already double-digit inflation rate and collapsing currency value. For a leader who prides himself on being able to say that he has all the answers, this economic strife keeps putting Erdogan's credibility into doubt. Turkey is moving sharply towards authoritarianism, but it remains a de facto democracy and public opinion matters on some level. In turn, Trump rightly judged that Erdogan would have to back down.

Still, it's likely that Trump's success here wasn't just rooted in his own confidence that Erdogan would back down, but also in Erdogan's confidence that Trump wouldn't blink. While the U.S. leader is judged abroad as highly unpredictable, he is also regarded as recalcitrant in his dealings. It's not just Turkey. Trump's reluctance to reach a trade deal with China, for example, is shocking to many global analysts who had expected Trump to blink by now. That resoluteness of spirit is useful in tough negotiations. Indeed, it is the most important basis for North Korea's consideration of a denuclearization deal: Kim Jong Un takes Trump's corollary threats at face value.

That said, there's one final factor here that might explain Erdogan's decision: the Turkish president's increasing realization that Russia has played him in Syria. Up until now, Erdogan had been maneuvering his nation's foreign policy toward the shelter of Vladimir Putin's umbrella. Hopefully, this deal reflects an Erdogan decision to rebuild relations with the United States. If so, the U.S. should help Erdogan shore up his economy.