On July 17, the United States finally decided to suspend Turkey’s participation in the F-35 fighter jet program, a move made in retaliation for Turkey’s acceptance of the Russian-made S-400 missile system. The U.S. decision was a fitting culmination to a drawn-out saga, which may well poison U.S.-Turkish ties for years to come.

It also laid bare the Trump administration’s failure to effectively implement one of the key provisions of the landmark Russia sanctions law enacted in 2017, the Countering America’s Adversaries Through Sanctions Act (CAATSA). Ultimately, the Trump administration’s own mixed signals contributed to President Recep Tayyip Erdogan’s calculation that he could proceed with the controversial acquisition without the risk of significant sanctions or damage to U.S.-Turkish ties.