Doug Bandow reviews  Trump’s many reversals:
When he was asked about the issue on CNN, he admitted, he deemed the organization obsolete “not knowing much about NATO, now I know a lot about NATO.” He argued that his ignorance was understandable “because I wasn’t in government. People don’t go around asking about NATO if I’m building a building in Manhattan, right?”
Right, but then, you don’t build a building in Manhattan if you don’t know anything about building a building. You learn about the process before you start. For the same reason, if you run for president, you expect to be asked about NATO, so you learn something about NATO. That’s what campaign advisers are for. That’s why candidates invite experts in for briefings. Except, apparently, candidate Trump.
Trump has a habit of showing off his ignorance of an issue and then later using that same ignorance to evade responsibility for previous statements that he made about it. When Trump claimed that NATO was obselete, many would-be supporters interpreted this to mean that he viewed the alliance as the outdated Cold War relic as they did, but that wasn’t his point at all. All he meant by that was that he thought the alliance should be involved in fighting terrorism, and he wrongly assumed that the alliance didn’t already do that. (He later claimed credit for “fixing” this.) Now that he is president and backtracks on the same claim, he admits what most observers already understood–that he is painfully ignorant of basic facts–and confirms that his ostensible anti-NATO posturing was just so much hot air.
Trump’s displays of ignorance may be remarkable, but especially on foreign policy this is what is bound to happen with a candidate who has no relevant experience or training in anything remotely related to these issues. Trump exacerbates his lack of preparation with his disdain for expertise and his tendency to reward flatterers, so that he remains poorly informed or thoroughly misinformed about major issues. That makes him almost uniquely susceptible to being taken in whatever direction his top advisers and officials want him to go, and Trump will be the last to know if they have been giving him smart advice or not.
All this should remind us that candidates with little or no foreign policy experience are the least likely to be successful in changing foreign policy to be less aggressive and more restrained. An ignorant candidate is the most easily misinformed and the least reliable. If that wasn’t obvious to everyone before, it ought to be now.