President-elect Trump just drew his first foreign policy red line with his tweet promising that development of a North Korean nuclear weapon capable of reaching the US “won’t happen!”. It is likely this line will be tested. How he responds will set the tone for his presidency, just as the firing of striking air traffic controllers did for Ronald Reagan. In fact the risks are much higher than they were for Reagan; the air traffic controllers were not armed with nukes.
Unlike many of Trump’s tweets, this one actually is in line with existing US policy. Despite this policy our actions towards North Korea were a bipartisan fiasco of appeasement and bribes during both the Clinton and Bush administration. President Obama has avoided getting caught in window-dressing negotiation with North Korea but he certainly hasn’t slowed their progress on development of either nuclear weapons or the means to deliver them. US red lines don’t have much credibility since Assad went unpunished for using chemical weapons on his own people (and everything he’s done since). According to the administration itself, Russia didn’t stop hacking after Obama told them to “cut it out” and that there would be “consequences”. It’s likely that Putin was more confident that he could get away with annexing Crimea than if he hadn’t had a chance to see us retreat from Obama’s red line in Syria.
It is obviously much, much better never to draw a red line than to draw it and then retreat from it. Obama didn’t have to say what he did about Syria. Trump didn’t have to tweet what he tweeted about North Korea. On the other hand, although we could stand aside in Syria, we really can’t let the mad man Kim Jung-un do what he threatens: “…tip new-type intercontinental ballistic rockets with more powerful nuclear warheads and keep any cesspool of evils in the Earth, including the U.S. mainland, within our striking range.” We will need to deal with this threat sooner rather than later; Trump would have been tested whether he tweeted or not.
Setting the red line and then enforcing it will give Trump credibility he can later use to stop other bad actors, perhaps just with words. What Trump does about North Korea will have much more effect on Putin’s behavior than whether he calls him a thug or a genius. Perhaps the most important audience for this red line exercise is Iran; will we or won't we hold them to the letter and spirit of the deal Obama made with them? Of course demonstrating that our word is reliable will also be a great relief to our allies.
But I don’t think words will stop Kim Jung-un and I hope Donald Trump doesn’t either.