Now that Donald Trump has exited the 2015 JCPOA nuclear deal with Iran, there is more at stake for the other signatories than either their belief in the deal’s virtues or their eagerness to salvage economic opportunities. Maintaining the deal without the US would deliver a severe blow to American credibility and perceptions of US power. China has long experience circumventing sanctions regimes, but the environment surrounding the reimposed sanctions is likely to be unusually confrontational.