On January 30, a Turkish court convicted Hamza Ulucay, an employee of the U.S. consulate in Adana, and sentenced him to 4.5 years in prison. Tried on groundless charges of “aiding an armed terror organization,” Ulucay was released on parole, having served nearly two years in pretrial detention. The mistreatment of Ulucay is the latest instance of President Recep Tayyip Erdogan’s “hostage diplomacy.”

Ulucay is one of three U.S. foreign service nationals (FSN) detained in Turkey in 2017 in the aftermath of the failed coup attempt of July 2016. Having declared a “state of emergency,” the Turkish government detained more than 150,000 people for allegedly partaking in the plot, ensnaring over 50 Western nationals, residents, and employees – including three U.S. nationals and three FSNs – in the process. Erdogan has since tried to use these political prisoners to extract concessions from his NATO allies.

Ulucay’s conviction was the second development concerning a Turkish FSN this month. On January 20, prosecutors demanded a life sentence for Metin Topuz, a Turkish translator and fixer for the Drug Enforcement Agency in the U.S. consulate in Istanbul. Topuz was detained in October 2017 on dubious charges of espionage and plotting a coup, and will have been in jail for a year and a half without ever seeing a judge until his first court appearance scheduled for March 26. Another U.S. consular employee, Mete Canturk, remains under house arrest in Turkey on similar charges.

Turkey’s hostage diplomacy brought the country to the brink of an economic crisis last summer. When Turkey refused to release U.S. Pastor Andrew Brunson, who had been jailed on farcical charges of espionage and terrorism for two years, President Donald Trump sanctioned two Turkish ministers under the Global Magnitsky Act and doubled the tariffs on Turkish aluminum and steel imports – sending the Turkish lira tumbling. Within months, Turkey released the pastor. But two other U.S. nationals remain in Turkey, a NASA scientist in prison and a chemistry professor barred from leaving the country.

Washington had also imposed sanctions on Turkey after authorities targeted its FSNs in the country. In October 2017, when Turkey detained Topuz and attempted to detain Canturk, the State Department temporarily suspended all visa services in Turkey. Ankara reciprocated, leading to the worst bilateral crisis between the NATO allies in decades. But Washington backed down after Turkey reportedly assured the U.S. that no other FSNs were under investigation, and both sides resumed visa processing within three months.

As President Trump seeks to subcontract his Syria policy to Turkey, Ankara’s treatment of U.S. nationals and FSNs is another reminder of the deep mistrust plaguing the bilateral relationship between the two countries. Lately, Erdogan appears to have released many of his European hostages and is reluctant to snatch new ones. But the Turkish president continues to double down on U.S. nationals and employees, most likely to use them as bargaining chips in his negotiations with Washington. Without a comprehensive strategy to address the Turkish strongman’s transgressions, Trump is set out for only disappointment.

Aykan Erdemir is a former member of the Turkish parliament and a senior fellow at the Foundation for Defense of Democracies, where Merve Tahiroglu is a research analyst. Follow them on Twitter @aykan_erdemir and @MerveTahiroglu. Follow FDD on Twitter @FDD. FDD is a Washington-based, nonpartisan research institute focusing on national security and foreign policy.