(CNN) Six presidential candidates took the stage in Des Moines, Iowa, for the last debate before voting begins in February. This debate's lineup was controversial. It was the first all-white debate stage of this election season.

Part 1

The start of the night was dominated by the crisis in Iran. While discussing the war in the Middle East, Sen. Bernie Sanders hit Joe Biden over his 2002 Iraq war vote.

Sanders doubled down on denying telling Sen. Elizabeth Warren that a woman couldn't win the presidency during a private 2018 meeting, which was revealed in a bombshell CNN report. Sen. Amy Klobuchar backed up Warren's response by laying out a defense for the electability of a female President.

Part 2

Health care reform has remained a hot-button issue throughout all seven debates so far. Candidates continued to spar over Medicare For All and the price tags for their proposed health care plans.

Part 3

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The climate crisis became a central talking point after former South Bend, Indiana, Mayor Pete Buttigieg listed the impending threats from the rapidly changing climate. Tom Steyer said he is "shocked" he is the only candidate currently in the race that calls climate change a No. 1 campaign priority.

Part 4

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The night came to a close as candidates reminded voters of why they were on stage and how they plan to defeat President Donald Trump.