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During two hours on a debate stage in Flint, Michigan, on Sunday, the two Democrats vying for their party’s presidential nomination spoke about race, education, gun control and infrastructure repair.

The subject matter touched on some of the most tender issues in American life, and the setting — a city reeling from an ongoing water crisis — made the discussion all the more urgent.

But there was one subject that didn't get any air time at all: foreign policy. ISIS was never mentioned. Nor was the air campaign over Iraq and Syria or the blossoming threat of ISIS affiliates in Libya.

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The omission was striking, given that Democratic front-runner Hillary Clinton is a former secretary of state. Sen. Bernie Sanders of Vermont has shown less comfort on these issues, but he has not been shy of criticizing Clinton for being too hawkish on foreign affairs.

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Sanders has often pointed to Clinton's vote in favor of authorizing the Iraq war while she served as a senator from New York and her role later in pushing President Barack Obama to launch an air campaign over Libya in 2011. Clinton is "too into regime change," Sanders said during a debate in October.

Related: Analysis: Hillary Clinton Denies Bernie Sanders a Win at Flint Debate

But Sunday, there were next to no fireworks on the issue. In the s opening minutes, Sanders briefly worked in a reference to the Iraq war, asking why the United States paid trillions of dollars for that war while it neglects problems at home.

"There are communities all over this country," Sanders said. "It's not just infrastructure. It is education. Detroit's public school system is collapsing."

According to a 2013 study by the Watson Institute at Brown University, the Iraq war cost $1.7 trillion. The study forecast nearly $500 billion more in benefits paid to veterans.

Sanders, who often refers to Iraq as an example of American overreach, has said his vote against authorizing the war shows that his judgment trumps Clinton's long experience in foreign affairs.