The six Democratic presidential candidates who debated Tuesday night in Des Moines agreed on one point: President Trump threw away a nuclear deal that was working and is now recklessly speeding toward war with Iran.
But they all turned vague when pressed on how they would accomplish their key goals — preventing Tehran from obtaining nuclear capability, stopping the revival of the Islamic State and disarming North Korea — without backing up diplomacy with the threat of military force.
Time and again, they separated themselves from Mr. Trump, especially on his rejection of allies and his unilateral action to pull out of international treaties and agreements. But they ended up describing a series of hopes for a return to negotiations and plans for incremental withdrawals that at moments echoed the Trump administration, circa 2019.
And all the candidates struggled to define the conditions under which they might use military force if there were no imminent threat, rejecting Mr. Trump’s “America First” approach to the world but trying to avoid stoking fears that they lacked the spine and strategic sensibilities to succeed as commander in chief.
The hedge words flew off the stage.
Asked whether he would never allow Iran to get a nuclear weapon, Pete Buttigieg, the former mayor of South Bend, Ind., said simply that ensuring the country remains far from obtaining one would “be a priority.” (Later, perhaps realizing he sounded less than decisive, Mr. Buttigieg, the only candidate on the stage who had served in the military, took a second shot and said American security “depends on ensuring that Iran does not become nuclear.”)
Former Vice President Joseph R. Biden Jr. conceded in the first minutes of the debate that it was a “mistake” for him to have voted for an authorization to use military force in Iraq 18 years ago, insisting that as soon he realized he had been deceived by George W. Bush’s administration he reversed course. After that, he said, he worked tirelessly to reduce the number of troops.
Then came the caveat. While he said he would not keep combat troops in the Middle East, he added that “I would leave troops in the Middle East in terms of patrolling the Gulf” and would keep a “small number” to confront the Islamic State. Those are both considerable tasks, in which a willingness to convince adversaries the United States would not leave the scene is often critical to backing up negotiations. And Mr. Biden said nothing about how he would respond if the Islamic State rose again, as it did after the withdrawals during the end of President Barack Obama’s administration.
Still, Mr. Biden staked his ground well to the right of Senator Elizabeth Warren of Massachusetts, who vowed that “it’s time to get our combat troops home” but never answered how the United States would help prevent the revival of the Islamic State without a ground presence.
The exchanges were all the more notable because until Tuesday night, foreign policy had been a side show in the 2020 campaign. But the targeted killing of the Iranian commander Maj. Gen. Qassim Suleimani this month ended the moment when the six Democratic candidates could avoid addressing some of the most complex and intractable conflicts that they would inherit if elected. Most seemed to be hoping the subject would soon return to more familiar ground, like universal health insurance or universal background checks for gun sales.
It should have been the moment for Mr. Biden to shine: A former chairman of the Senate Foreign Relations Committee, he was among the most experienced in the Obama Situation Room during debates over increasing troop levels in Afghanistan and secretly carrying out cyberattacks on Iran’s nuclear facilities.
He had a moment to look decisive, especially in contrast to Senator Bernie Sanders of Vermont, who was the most vociferous about extracting the United States from what he called “endless wars.” Again, it echoed a phrase that Mr. Trump has often used — or at least did until his decision to kill General Suleimani all but assured a greater American troop presence in the Middle East for years to come.
Mr. Biden was clearly the one with the best grasp of the global situation, but he seemed unsteady at moments, even when describing events in which he was deeply involved. He argued that he was the one who “led the effort” against “surging tens of thousands of troops into Afghanistan,” without noting that Mr. Obama ignored his advice and ordered a surge anyway. On Iraq, he claimed he was the one who engineered the withdrawal of 156,000 troops from Iraq without noting that it was Mr. Bush, just before leaving office, who ordered a troop withdrawal.
But it was on North Korea — a nation that, unlike Iran, is already believed to have nuclear weapons, with American intelligence agencies putting the number at 30 to 60 — that the candidates seemed softer. Curiously, none vowed that the North would have to give up its weapons, a statement that just a decade ago was a staple of any foreign policy discussion by leading presidential candidates, even if it seemed like a pipe dream.
Instead, the candidates seemed to silently acknowledge that disarming the North was all but a lost cause. Instead, they focused on negotiating tactics, without ever quite saying what the goal would be. Mr. Biden vowed he wouldn’t meet Kim Jong-un, the North Korean leader, “without any preconditions,” but never described what those might be.
What was most striking about the discussion was that the candidates talked about the use of diplomacy and military coercion as if they were alternatives, rather than mutually reinforcing tactics to accomplish a strategic end.
Such concepts can seem too abstract amid the bumper-slogan imperatives of a presidential debate. But it left the candidates seeming to revert to caricatures of themselves: Mr. Sanders and Ms. Warren trying to outdo each other on the speed with which they would withdraw troops and Mr. Biden and Mr. Buttigieg carefully leaving themselves room to keep modest amounts of American power in the region.
Only Mr. Buttigieg touched on the changing nature of warfare, suggesting that while the debate over the Iraq war struck a nerve, it had little to do with the national security challenges the next president would face.
Those were “not just conventional military challenges,” he said, “not just stateless terrorism, but cybersecurity challenges, climate security challenges, foreign interference in our elections.” It seemed an effort to contrast himself with Mr. Trump, who has a 1950s view of American power — often measuring it by naval tonnage and nuclear arsenals.
But it was Iran that animated the conversation and gave each candidate a chance to differentiate his or her approach from Mr. Trump’s.
Several candidates said they would re-enter negotiations with Iran on a new version of the 2015 deal, with what Mr. Biden said would be changes to assure Iran could not return to producing nuclear fuel for many more years, and with heightened inspections.
But he never explained what would drive the Iranians back to the table, or persuade them to take a less advantageous deal than the one the country’s leadership negotiated, over nearly three years, with the Obama administration. Would the candidates lift sanctions on Iran first, in hopes that would encourage the country to return to the old deal? None said. Would they deploy military assets to make it clear the United States would destroy nuclear facilities in case diplomacy failed?