Bernie Sanders speaks to supporters about foreign policy in March in Salt Lake City. (Photo: John Locher/Associated Press)

Bernie Sanders doesn’t know whether President Obama’s signature counterterrorism strategy, drone strikes, is the right approach to the problem. Fifteen years into a bitter national debate about Guantanamo Bay, he hasn’t thought much about where he would imprison and interrogate a captured terrorist leader. He can’t explain his call for Israel to pull back from some settlements on Palestinian land because he doesn’t have “some paper” in front of him. He also can’t say why he doesn’t support Palestinians taking action against Israel before the International Criminal Court.

Those are all takeaways from a New York Daily News interview with Sanders, whose long-shot campaign for the Democratic presidential nomination has surprised many observers by mounting a real challenge to former Secretary of State Hillary Clinton.

The Vermont senator’s potent message to voters in 2016 has focused on economic issues, arguing that the very rich have rigged the system in their favor with the help of venal politicians. He has marketed himself as the candidate who will upend the system and has leveraged that appeal into an unlikely string of primary victories, in part thanks to a well-organized campaign ground game and an online machinery that is without peer in the Senate.

He never intended to focus on international relations.

As late as August 2015, when Yahoo News looked at how Sanders would handle foreign policy, his official campaign website did not even have a section on world affairs — though his team has since added one. Sanders has relied on one weapon in his national security duel with Clinton: She voted in favor of authorizing George W. Bush to go to war in Iraq; he voted against it. That argument worked for Obama in 2008, the senator’s aides seem to think, so why not now?

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Clinton, who rarely misses a chance to refer to her crisis meetings with Obama in the White House Situation Room and peppers her national security remarks with names of foreign leaders she has met, isn’t invulnerable on foreign policy. Far from it.

But what the awkward Daily News interview confirms is that she has little to fear on that score from the iconoclastic senator from Vermont.

The April 1 question-and-answer session came just a couple of weeks after Sanders laid out his Middle East policy in a detailed speech in Utah that seemed designed to show fluency in world affairs, whatever one might think of the policy particulars. There were common themes to both sets of remarks — defeating the Islamic State requires Muslim ground troops, Middle East peace requires compromises from all sides, etc. But the Sanders who turned up for the interview seemed to have lost fluency on some central questions for candidates vying to be commander in chief.

Sanders repeated his call for Israel to hold off from building new settlements in the West Bank and to pull back from some existing ones that he called “illegal.”

The Daily News asked how much Israel should pull back.

“You’re asking me a very fair question, and if I had some paper in front of me, I would give you a better answer,” Sanders replied. “But I think if the expansion was illegal, moving into territory that was not their territory, I think withdrawal from those territories is appropriate.”

So, if the United States were to determine that some settlements are illegal under existing treaties and agreements, then a Sanders administration would expect Israel to pull back?

“Israel will make their own decisions,” Sanders replied.

The Daily News continued, asking him if he supports the Palestinian leadership’s efforts to drag Israel before the International Criminal Court over alleged war crimes.

No, said Sanders.

“Why not?” the Daily News asked.

“Look, why don’t I support a million things in the world? I’m just telling you that I happen to believe,” said the senator, who went on to say that Israel’s military had engaged in indiscriminate bombings of Palestinians but never said why he opposed bringing in the ICC.

Turning to drone strikes, the Daily News incorrectly said Obama had taken the program away from the CIA and given it to the military, then noted the yearslong controversy over the tactic.

“Do you believe that he’s got the right policy there?” the editorial board asked.

“I don’t know the answer to that. What I do know is that drones are a modern weapon,” Sanders said.

The senator noted that civilian casualties from drone strikes undermine U.S. goals and urged that “whoever is in control of that policy, it has to be refined so that we are killing the people we want to kill and not innocent collateral damage.” (Sanders would have been on firmer ground simply by starting his answer with the mixed assessment he delivered, which echoes some of Obama’s own public remarks about drones.)

Marines and a detainee at Camp X-Ray at Guantanamo Bay, Cuba, in 2002. (Photo: Marc Serota/Reuters)

Where would a Sanders administration imprison and interrogate a captured Islamic State commander?

“Actually I haven’t thought about it a whole lot,” the senator answered. Sanders went on to say that such prisoners should be held in a safe, secure locale, ideally not far from where they were captured, and that he was open to jailing them on U.S. soil.

That’s seen as a necessary position for anyone who supports closing the detention center for suspected extremists at Guantanamo Bay, Cuba. Sanders the presidential candidate supports doing so, while Sanders the senator’s record is mixed.

Sanders isn’t as much of a foreign policy cipher as his opponent and many commentators suggest. He’s not a pacifist, and while he tends to oppose military interventions, he backed the 2001 invasion of Afghanistan and voted in favor of giving President Bill Clinton the authority to carry out airstrikes against Serbian targets in Yugoslavia in 1999. He supports the Iran nuclear deal. He opposes Obama’s sweeping trade agreement with Pacific nations. He’s more supportive of the president’s approach to Syria than Clinton, who has called for establishing and defending no-fly zones and repeatedly noted that she favored arming Syrian rebels while Obama did not.

But with the Daily News interview, Sanders played into the hands of critics who charge he simply isn’t interested in or informed about foreign affairs. The Clinton campaign didn’t hesitate to send the transcript of Sanders’ interview to its mass email list.