(Bloomberg) — Joe Biden and Bernie Sanders confronted each other over the use of military force in the Middle East Tuesday, as Democratic candidates for president argued over the Iraq war amid rising tensions in the Middle East.Senator Sanders called the Iraq war “the worst foreign policy blunder in modern American history” and attacked Biden for voting to authorize it. Biden said the vote in 2002 was a mistake but that as vice president under Barack Obama he would compare his record to anyone else’s.Sanders opposed the Iraq war but voted in favor of the war in Afghanistan. Biden said his Iraq war vote was a “big, big mistake” but that he later sought to prevent a surge in troops.From Iran to North Korea to nuclear proliferation, foreign policy dominated the first segment of the Des Moines Register/CNN debate as it hasn’t in six previous debates. The first question tested each candidate on their qualifications as commander-in-chief. That’s been a selling point for Biden, but his past foreign policy positions have come under new scrutiny — from the right and the left — for his support of the wars in Afghanistan and Iraq.The Democratic candidates have all opposed President Donald Trump’s decision to kill Iranian General Qassem Soleimani this month, saying it threatened to further destabilize the region.All the candidates argued for a diminished U.S. military role in the Middle East, but differed on how far they would go. Biden said there was a role for special forces working with allies, but Sanders and Senator Elizabeth Warren said they would pull out completely.“We should stop asking our military to solve problems that cannot be solved militarily,” Warren said.Former South Bend, Indiana Mayor Pete Buttigieg, a veteran of the Afghanistan war, said U.S. involvement should be limited, proposing that Congress should have to renew its authorization for military force every three years.Going into the debate, all eyes were on the two progressive candidates standing on either side of Biden: Sanders and Warren.The two senators maintained a united front through all six debates last year, but recent squabbles over who should be the standard-bearer for the party’s left flank have tested their alliance.They’re competing with Biden and Buttigieg in a competitive four-way battle for the 2020 presidential campaign’s first contest: the Iowa caucuses on Feb. 3. Also participating in the debate were Senator Amy Klobuchar of Minnesota and billionaire investor Tom Steyer.While the Democratic primary started with the most diverse field of candidates in history, only white candidates made it to Tuesday’s debate stage. Cory Booker dropped out of the race on Monday while Andrew Yang, Tulsi Gabbard and Deval Patrick all missed the polling and fund-raising requirements to qualify for the January debate.Former New York Mayor Mike Bloomberg is self-funding his presidential campaign so he didn’t meet the donor requirement to participate. Bloomberg is the founder and majority owner of Bloomberg L.P., the parent company of Bloomberg News.Tuesday’s debate is the last such forum before the Iowa caucuses. It’s particularly important for the senators — Sanders, Warren and Klobuchar — who will have to break away from campaigning as soon as this week to be sworn in as jurors in Trump’s impeachment trial. After that, the trial could require their presence at the Capitol for weeks to come.To contact the reporters on this story: Gregory Korte in Washington at firstname.lastname@example.org;Misyrlena Egkolfopoulou in Washington at email@example.comTo contact the editors responsible for this story: Wendy Benjaminson at firstname.lastname@example.org, Larry LiebertFor more articles like this, please visit us at bloomberg.com©2020 Bloomberg L.P.