(Russian Defense Ministry Press Service pool photo via AP) The U.S. has imposed long-anticipated economic sanctions on Turkey for their purchase of the Russian S-400 mobile surface-to-air anti-aircraft missile system. A NATO ally, Turkey’s action undermined the alliance’s defenses. The S-400 may be the only weapons platform outside of NATO that could shoot down America’s most advanced fighters, including the F-35. Turkey’s President Recep Erdogan made the purchase to better protect itself from wars raging on its borders and to make the country’s defense industry more self-sufficient. But clearly, the decision to make the purchase was political. Turkey is making a statement about its sovereignty within NATO and other NATO nations are listening.