Exactly one year after the Trump administration pulled out of the Iran nuclear deal, tensions between Washington and Tehran are escalating sharply amid confusion about what, exactly, the U.S. sees as its end goal. For Iran, uncertainty about President Donald Trump’s aims presents a menu of risky choices.

The U.S. and Turkey have engaged in extensive diplomacy to try and resolve the festering dispute over the Turkish government’s decision to buy the advanced S-400 missile defense system from Russia. How this issue is resolved, if at all, could permanently alter the trajectory of U.S.-Turkey relations.