about the use of military force and how and when they would deploy if they become president.

This weekend, the Democrats hoping to unseat the current commander in chief have been weighing

in on his pivotal decision to strike out at a top Iranian commander.

Amna Nawaz begins there.

AMNA NAWAZ: In a Democratic primary race dominated by domestic issues, it was issues of war and

peace overseas this weekend that deepened fault lines in the field.

SEN. BERNIE SANDERS (I-VT), Presidential Candidate: War is the last response to international

conflict, not the first.

(CHEERING AND APPLAUSE)

AMNA NAWAZ: Vermont Senator Bernie Sanders has been the sharpest critic so far of the

Trump-directed airstrike that killed top Iranian military leader Qasem Soleimani.

An Iraq War veteran in Dubuque, Iowa, asked Sanders how he'd prevent another war in the

region as president.

Sanders, in warning against future U.S. involvement in the Middle East, highlighted his own record

on these issues.

SEN. BERNIE SANDERS: I not only voted against the war in Iraq. I helped lead the opposition

to the war in Iraq.

AMNA NAWAZ: In particular, a difference with former Vice President Joe Biden.

Candidate Biden has been stressing his foreign policy experience on the campaign trail. In

Des Moines this weekend, he claimed that he opposed the Iraq War -- quote -- "from the

very moment" the Bush administration started that military campaign.

JOSEPH BIDEN (D), Presidential Candidate: I opposed what he was doing, and spoke to

it.

AMNA NAWAZ: But as senator in 2002, Biden voted for the war in Iraq, voicing his opposition

in the years that followed.

Biden agreed that Soleimani's alleged crimes warranted the U.S. targeting him. Still, Biden

questioned the Trump administration's long-term Middle East strategy.

JOSEPH BIDEN: This is a crisis totally of Donald Trump's making.

AMNA NAWAZ: Former Mayor Pete Buttigieg, a former Naval intelligence officer who served

in Afghanistan, took a similar approach.

PETE BUTTIGIEG (D), Presidential Candidate: Now, let's be clear, Qasem Soleimani was a

bad figure. He has American blood on his hands. None of us should shed a tear for his death.

But just because he deserved it doesn't mean it was the right strategic move.

SEN. ELIZABETH WARREN (D-MA), Presidential Candidate: We don't need more war in the Middle

East.

AMNA NAWAZ: Massachusetts Senator Elizabeth Warren, who walked back her initial strong

support for the airstrike, this weekend questioned its timing.

In an NBC interview, she suggested the president was trying to distract from other issues.

SEN. ELIZABETH WARREN: We are not safer because Donald Trump had Soleimani killed. We are

much closer to the edge of war. I think the question people reasonably ask is, next week,

Donald Trump faces the start potentially of an impeachment trial. And why now? I think

people are starting to ask, why now did he do this?

AMNA NAWAZ: The new questions about force and foreign affairs come less than one month

before the Iowa caucuses.

A new CBS News poll shows a three-way tie in Iowa among Sanders, Biden and Buttigieg,

with Warren lagging in fourth. But she also got a boost today from a former primary rival:

JULIAN CASTRO (D), Former Presidential Candidate: There's one candidate I see who's unafraid

to fight like hell.

AMNA NAWAZ: An endorsement from former Housing Secretary Julian Castro, who was the primary

field's only Latino candidate before leaving the race last week. He is scheduled to join

Warren on the trail tomorrow in New York City.

For the "PBS NewsHour," I'm Amna Nawaz.