Thursday afternoon, Reuters reported that Donald Trump interrupted a phone call with Vladimir Putin to ask a basic question about US-Russia relations. Specifically, he asked what New START, a nuclear arms agreement inked by the Obama administration, was. Once he heard the basics, he immediately informed Putin that he was against it.

“When Putin raised the possibility of extending the 2010 treaty, known as New START, Trump paused to ask his aides in an aside what the treaty was,” the Reuters reporters, Jonathan Landay and David Rohde, write. “Trump then told Putin the treaty was one of several bad deals negotiated by the Obama administration, saying that New START favored Russia. Trump also talked about his own popularity.”

Three things stick out about this report, presuming it’s accurate (both Rohde and Landay are skilled veterans of the national-security beat, and the White House has declined to comment on the report both to Reuters and when asked during a subsequent press briefing). The first is that Trump still clearly does not know basic facts about American foreign policy, like the name of a major treaty — and that this somehow leaked to the press from one of his top advisers, the only people in the room for the Putin call.

The second is that the president seems willing to make major policy changes anyway. Trump had referenced New START in an October presidential debate, though he called it “start up” and incorrectly suggested that it limited American nuclear warhead construction without similarly capping Russia’s. (The deal actually caps each country’s number of deployed nuclear warheads at 1,550.)

Months later, after winning the presidency and having daily national security meetings, Trump still doesn’t know the treaty’s name. But he decided to come out against it anyway after getting quick refresher while Putin was on hold.

Finally, the comments seem to contradict stuff Trump has said recently about nuclear weapons. Just days before his inauguration, Trump said in an interview that he hoped to work with Russian strongman Vladimir Putin to reduce both countries’ nuclear arsenals.

“Let’s see if we can make some good deals with Russia,” Trump said at the time. “For one thing, I think nuclear weapons should be way down and reduced very substantially.”

Those comments, in turn, directly contradicted a December tweet, where he said that the US “must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes.” Afterwards, MSNBC’s Mika Brzezinski asked him about the possibility of this policy setting off an arms race with Russia (which is also talking about modernizing its nuclear arsenal). She recalls Trump’s answer being simple.

“Let it be an arms race.”

There’s only one reasonable conclusion to draw from all this: The president’s positions about the only weapon capable of destroying human civilization seem to be in constant flux — and sometimes change on the dime while the leader of the country with the world’s second-biggest nuclear arsenal is still on the phone.

The strange history of Trump on nuclear weapons

Questions about nuclear policy have dogged Trump for more than a year now. In a December 2015 Republican debate, moderator Hugh Hewitt asked Trump about the “nuclear triad” — America’s three-part system for delivering nuclear weapons (bombers, submarines, and intercontinental ballistic missiles). Trump’s answer was confusing:

We have to be extremely vigilant and extremely careful when it comes to nuclear. Nuclear changes the whole ballgame. … The biggest problem we have is nuclear — nuclear proliferation and having some maniac, having some madman go out and get a nuclear weapon. That's, in my opinion, that is the single biggest problem that our country faces right now.

There are two interesting things about this. First, Trump suggests, as he later did in his January interview, that he sees large global nuclear stockpiles as a problem. Second, he doesn't appear to know any of the major policy questions surrounding the nuclear triad, or even what the nuclear triad is.

That became especially clear when Hewitt followed up, pressing Trump to answer the actual question about the triad. Trump’s response? “I think — I think, for me, nuclear is just the power, the devastation is very important to me."

This pattern — an abstract abhorrence of nuclear weapons but seemingly confused views on actual nuclear policy — continued throughout the campaign. In a March 2016 town hall, host Chris Matthews pressed Trump on whether he’d use nuclear weapons. He seemed to say both no and yes at the same time, saying he’d be “the last one to use nuclear weapons,” but also that he would be willing to nuke ISIS territory in response to a terrorist attack:

TRUMP: I’d be the last one to use the nuclear weapons, because that’s sort of like the end of the ballgame. MATTHEWS: So, can you take it off the table now? Can you tell the Middle East we are not using the nuclear weapon on anybody? TRUMP: I would never say that. I would never take any of my cards off the table… MATTHEWS: Where would we drop — where would we drop a nuclear weapon in the Middle East? TRUMP: Let me explain. Let me explain. Somebody hits us within ISIS — you wouldn’t fight back with a nuke?

In August, MSNBC host Joe Scarborough recounted a story an unnamed foreign policy expert told him about Trump and nukes. In it, Trump expresses confusion as to why the US doesn’t use its nukes.

"Several months ago, a foreign policy expert on the international level went to advise Donald Trump. And three times [Trump] asked about the use of nuclear weapons. Three times he asked at one point if we had them why can't we use them," Scarborough said.

During the first general election debate, in September 2016, moderator Lester Holt asked a more specific version of Matthews’s question — what Trump thought about a “no first use” policy. That’s the idea that the US should swear off launching a nuclear strike against an enemy unless it has been attacked with nukes first.

Here was Trump’s answer:

Russia has been expanding their — they have a much newer capability than we do. We have not been updating from the new standpoint. I looked the other night. I was seeing B-52s, they're old enough that your father, your grandfather could be flying them. We are not — we are not keeping up with other countries. I would like everybody to end it, just get rid of it. But I would certainly not do first strike. I think that once the nuclear alternative happens, it's over. At the same time, we have to be prepared. I can't take anything off the table.

Trump’s answer, once again, gestures at hating nuclear weapons (“just get rid of it”). But he also implies that he supports developing more advanced ways of delivering nuclear weapons — which the US is already doing.

But when it came to Holt’s actual question, about his views on no first use as a policy, Trump had no real answer. He’s said both, “I would certainly not do first strike,” and, “I can’t take anything off the table” — but those are opposite things. The whole point of a no-first-strike policy is taking a first strike off the table. That means Trump literally had never heard of the no-first-use debate, had never thought about it enough to have an actual opinion, or for some reason didn’t want to say that that opinion was.

His reference to the “start up” treaty came in the third presidential debate.

“Putin has outsmarted [Clinton] and Obama at every single step of the way. Whether it's Syria, you name it. Missiles,” Trump said. “Take a look at the ‘start up’ that they signed. The Russians have said, according to many, many reports, I can't believe they allowed us to do this. They create warheads, and we can't. The Russians can't believe it. She has been outsmarted by Putin.”

By the time Trump won the election, experts on nuclear policy were thoroughly confused. There was simply no consistent policy through-line, no meaningful ability to figure out what Trump truly plans to do with the only weapons that have the power to destroy the Earth in minutes.

“To journalists asking me what nuclear policies Trump will adopt: I have absolutely no idea,” James Acton, the director of the Carnegie Endowment for International Peace’s Nuclear Policy Program, wrote two days after Trump’s upset win. “And neither, I strongly suspect, does he.”

Trump’s actual nuclear policy has not gotten clearer

If you squint at this history of Trump comments, you can kind of put together a consistent line.

It seems that Trump thinks nuclear weapons are extremely dangerous and that the world should work on eliminating them. But in the absence of any agreements to do so, the United States should maintain and even expand its nuclear arsenal to make sure it’s deadlier than that of any peer competitor.

Read in this light, there’s some consistency between Trump’s December and January lines. In December, he was expressing what the US should do absent arms control agreement: Expand and upgrade its nuclear stockpile. In January, by contrast, he was expressing his support for an agreement between the US and Russia that might make this unnecessary.

These views have some foundation in real policy problems. As my colleague Yochi Dreazen explains, there’s a widespread worry in the national security community that America’s system for delivering nukes is starting to show cracks — to take one high-profile example, an investigation found that missileers at one base in Montana were routinely cheating on their proficiency exams, meaning they might not actually be able to launch. Failures like this, and the need to make sure nukes actually function, led the Obama administration to devote about $1 trillion over the next 30 years to nuclear maintenance and growth.

But it’s very hard to square this set of views with his criticism of New START. The treaty really does limit each country’s nuclear arsenals — which is why Trump’s new secretary of state, Rex Tillerson, is a fan.

“[It’s important to] stay engaged with Russia, hold them accountable to commitments made under the New START and also ensure our accountability as well,” he said during his Senate confirmation hearing.

The easiest way to square this circle is to assume that Trump’s view of New Start comes less from any thought-out view of nuclear policy and more from the fact that it was an Obama administration agreement, and therefore automatically a bad idea. But that, needless to say, is a very bad way to formulate nuclear policy.

If that’s what Trump is really doing, Reuters’ account doesn’t clarify the actual policy stance that follows from Trump’s comments to Putin. Is he thinking of withdrawing from New START? Renegotiating it? Who knows!

This lack of clarity extends to other key nuclear policy issues. Does Trump now support a no-first-use doctrine? Does he support entirely eliminating nuclear weapons, a goal known as “global zero,” or merely further reductions in the US and Russian stockpiles? What about the Anti-Ballistic Missile Treaty or the Comprehensive Test Ban Treaty, two major nuclear policy agreements?

“It's difficult to discern what Trump's policy will be and whether he has given more than a few minutes’ thought to these issues,” Kingston Reif, the director for disarmament and threat reduction policy at the Arms Control Association, told me in a message around the time of Trump’s inauguration. Things haven’t gotten any clearer since.

Watch: How Putin won Republicans’ approval