There is an unwritten code of conduct among American diplomats that says they should never say anything that is untrue or inaccurate. They are not required to say everything they know because they must also keep secrets. But it is central to their mission to be truthful--not as a "moral" obligation but as a fundamentally practical one. The legendary American journalist Edward R. Murrow best expressed the rationale for American diplomats when he said, "To be persuasive we must be believable; to be believable we must be credible; to be credible we must be truthful. It is as simple as that."
U.S. diplomats depend for their success on building trust with foreigners and other people they deal with in their work. To achieve that trust, they must establish a reputation of never deliberately misleading anyone by saying something that can turn out to be false.
This is especially true of senior officials in Washington and American diplomats working at U.S. embassies abroad who engage in "public diplomacy" when they speak out in public. Their words carry official weight so they must be very careful what they say, and they are careful to be truthful and accurate.
With the 2016 presidential election, American diplomats have two new problems in carrying out their task of explaining United States policy. One chronic problem is that the president has repeatedly said things that have turned out to be untrue. A second problem is that the president has made statements that later seem to be contradicted or modified by senior members of his administration. American diplomats have always operated on the assumption that what the president says is, by definition, official policy, and they expect all other US officials to follow the president's line, whatever it is. But it turns out that a major handicap for American diplomats today is that the current administration is sending confusing and often contradictory signals on what U.S. policy is.
The most recent example of this disconnect is U.S. policy on North Korea. In early August, after North Korea threatened to fire missiles in the direction of the US territory of Guam, President Trump issued a strong threat to Pyongyang. He said, "North Korea best not make any more threats to the United States. ... They will be met with fire, fury and frankly power the likes of which this world has never seen before." Did this mean he was preparing to go to war as a response to more threats? North Korean then did...