It would be safe to say that U.S. allies were just a wee bit nervous about the NATO summit in London this week. On Monday, my Post colleague Michael Birnbaum detailed the myriad ways the summit was being engineered to prevent a repeat of the less-than-perfect 2017 and 2018 summits. According to Birnbaum, this time around, “every last detail of this anniversary get-together has been choreographed to ensure that Trump’s happiness will be maximized and any opportunities to blow up the program, or the alliance, minimized.” That included scrubbing the formal dinner and condensing the traditional two days of meetings into a single three-hour session. Birnbaum was hardly the only reporter to detect this nervousness from U.S. treaty allies in the run-up to London.

The actual summit is Wednesday, and the odds of Trump behaving well at one of these functions is not good. Still, on Tuesday, there was some rather remarkable behavior by the president of the United States. First, according to my Post colleagues Ashley Parker and Philip Rucker, “President Trump on Tuesday slammed as ‘very, very nasty’ and ‘very disrespectful’ recent comments by his French counterpart about the diminished state of the North Atlantic Treaty Organization alliance. … ‘You just can’t go around making statements like that about NATO.’ Trump said.”

I’ve bolded that sentence in the previous paragraph because Trump has spent most of his political life making statements like that against NATO. So this is certainly some odd rhetoric coming from Trump.

If you watch the video, it’s apparent that for once Trump and Angela Merkel agree on something: They are both quite put out with French President Emmanuel Macron and his comments about NATO being brain-dead. It sure seemed like Trump’s meeting with Macron would be a blockbuster.

Instead, according to the New York Times’s Katie Rogers and Annie Karni, something altogether different played itself out:

By the time their 45-minute appearance at the American ambassador’s residence in London was over, the French leader had managed a rare role reversal, putting Mr. Trump on the defensive about his vision for NATO and his handling of a military conflict involving Turkey, and swatting away the president’s joke about sending Islamic State fighters from Syria to France …
When asked during the afternoon meeting to address his earlier comments about Mr. Macron, Mr. Trump, a leader averse to face-to-face confrontation, initially demurred. When it was his turn to speak, Mr. Macron was direct.
“My statement created some reactions,” Mr. Macron said. “I do stand by it.” …
Mr. Trump slumped back in his chair, while Mr. Macron sat on the edge of his chair, bobbing and gesturing energetically.
Mr. Macron’s aggressive approach appeared at times to unsettle Mr. Trump.

What happened? What the heck is going on? Allow me to proffer one hypothesis using some important documentary footage about how to negotiate with someone possessing a similar psychological profile to Donald Trump:

As New York’s Jonathan Chait observed, “Manipulating children into doing what you want by pretending to demand they do the opposite thing is a trick most parents learn to use. It usually stops working around the age of 5.”

Trump is biologically older than 5, but his oppositional behavior has been prominent throughout his political life. During the 2016 campaign, Howard Kurtz reported that Trump’s aides labeled this “defiance disorder.” In 2017, Axios’s Mike Allen reported, “Aides say the quickest way to get Trump to do something is to tell him he can’t.” There’s an entire chapter in my forthcoming book devoted to how Trump’s oppositional behavior is akin to that of a toddler.

So is it that simple? Did Macron figure out that the way to get the best of Trump is to exploit his psychological weaknesses such as defiance disorder and an abhorrence of direct confrontation to get him to support NATO?

It’s not quite that simple. Politico’s David M. Herszenhorn suggests that NATO Secretary General Jens Stoltenberg also deserves some credit, as he has spent the past three years doing what he can to make Trump happy. There is something to that, although the degree to which Stoltenberg has attempted to please Trump seems like toddler psychology as well.

There is another alternative, however. Trump needs NATO because he is running for reelection and does not have other global deals to point to as successes. My Post colleague Toluse Olorunnipa pointed out that on the same day Trump tried to play nice on NATO, he was in the awkward position of saying that the phase one trade deal with China that he announced as done two months ago might not actually be done until a year from now:

As Trump campaigns for reelection, he has abandoned more deals than he has struck, and his boasts about eager negotiating partners could face scrutiny from voters who expected more results from the self-described master dealmaker, said Barbara Perry, a presidential historian at the University of Virginia’s Miller Center of Public Affairs.
“Three years into his term, are there going to be people who say, ‘He promised me X, and I didn’t get it, and now I’m not voting for him’?” she said. “It’s certainly a high-wire act.”
In some cases, other countries have flatly contradicted Trump or expressed surprise about his assertions, indicating that some of his claims of favorable negotiating conditions are more wishful thinking than reality.

Trump needs to be able to say he wrung more defense spending from NATO allies because when it comes to international dealmaking, he does not have a lot more to be able to campaign on. This requires him to stop haranguing NATO and declare mission accomplished.

What will be interesting to see is whether other leaders, sick of flattering Trump with little to show from it, follow Macron’s example. There is another possibility, however: Trump reads stories about Macron getting the best of him and throws a temper tantrum at the actual meeting. With Trump, one is never entirely certain which toddler trait will come to the forefront.