Lucy Nicholson / Reuters

Bernie Sanders didn’t prepare much for Tuesday night’s Democratic presidential debate. And on foreign policy, it showed.

It began when Anderson Cooper asked the Vermont senator “what would you do differently” than Hillary Clinton about the conflict in Syria. Sanders answered that, “We should be putting together a coalition of Arab countries who should be leading the effort. We should be supportive, but I do not support American ground troops in Syria.” Which is fine, except that Hillary also supports an Arab coalition and also opposes ground troops, so Sanders didn’t answer the question.

A bit later, CNN’s Dana Bash asked Sanders “under what circumstances would a President Sanders actually use force?” To which Sanders replied that unlike Hillary, he opposes “a no-fly zone in Syria, which I think is a very dangerous situation, [and] could lead to real problems.” In other words, he answered the previous question but not the one he had just been asked.

So Cooper tried again: “Senator Sanders, you didn't answer the question. Under what—under what circumstances would you actually use force?”

To which Sanders replied: “When President Clinton said, ‘let’s stop ethnic cleansing in Kosovo,’ I voted for that. I voted to make sure that Osama bin Laden was held accountable in Afghanistan. When our country is threatened, or when our allies are threatened, I believe that we need coalitions to come together to address the major crises of this country. I do not support the United States getting involved in unilateral action.”

There are a couple of problems with that answer. First, Sanders says he supports “coalitions” when “our country is threatened, or when our allies are threatened.” But he also says he supported NATO’s campaign in Kosovo, a war America fought on humanitarian grounds despite the fact that Yugoslav President Slobodan Milosevic threatened neither America nor its allies. Second, declaring categorically that, “I do not support the United States getting involved in unilateral action” is also a pretty remarkable thing to say. Yes, multilateral action is wiser. But if the United States were directly threatened, would Sanders really rule out a military response unless other countries joined in? Is that the test he would have applied after 9/11? A plain reading of his words suggests the answer is yes.

Later, Sanders suggested that “Mr. Putin is going to regret what he is doing” in Syria. When Cooper replied that, “He doesn’t seem to be the type of guy to regret a lot,” Sanders responded that, “I think he’s already regretting what he did in Crimea and what he is doing in the Ukraine.” But the evidence suggests the opposite. Vladimir Putin’s approval ratings spiked dramatically in early 2014, when his forces took Crimea. And as of this summer, they remained just as high, despite the fighting in Ukraine and despite Western economic sanctions against Russia. Russia expert Dimitri Simes argues that, since two-thirds of Russians believe Western sanctions are designed to “weaken and humiliate” the country, Russians have “rallied around the flag and embraced Putin” in response.

Sanders may be right that Putin’s actions in Syria will come back to haunt him. He’s certainly right that the United States should not plunge further into Syria just to show that America, and not Russia, still dominates the Middle East. But citing the annexation of Crimea to show Putin has learned that aggression doesn’t pay is deeply unconvincing.

Sanders’s discomfort with these issues is not new. In early September, he actually apologized during a meeting at The Des Moines Register for not having a better-developed foreign-policy platform. Until last month, his campaign website didn’t say anything about foreign policy at all.

This discomfort matters, and not just for his presidential hopes. Hillary Clinton is moving to the political left on just about every domestic issue, yet positioning herself to Barack Obama’s right on foreign policy. In so doing, she’s making it almost inevitable that American foreign policy will grow more hawkish in the post-Obama era, even though that’s not what most Democrats want. According to a Pew Research Center poll earlier this year, for instance, Democrats were more than twice as likely to worry that America “will go too far in getting involved” in Iraq and Syria than to worry that America “will not go far enough in stopping the Islamic militants.” If Sanders could challenge Hillary more convincingly on foreign policy, he’d air an important debate about how much of a threat events in Syria and Iraq pose to the United States—and whether further American military intervention will stabilize the Middle East, or further destabilize it. He’d also be the one major candidate in either party challenging the pervasive, and to my mind untrue, narrative that under Obama, America’s retreat has sparked chaos around the world.

Between now and the next debate, let’s hope he studies more.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.