Editor's Note: This article originally appeared on Business Insider.

Former Defense Secretary Jim Mattis slept in his clothes because of North Korea's missile launches amid the U.S.'s rocky relations with the regime in 2017, according to a new book on the Trump administration.

The account comes from CNN's review of Bob Woodward's upcoming book, Rage, which is scheduled for release on September 15.

According to the book, U.S.-North Korean relations were fragile and the potential for nuclear war was on the mind of the president's national security staff. Pyongyang fired roughly two dozen missiles in 2017, including its highest-ever intercontinental ballistic missile, shortly after Donald Trump became president.

As North Korean leader Kim Jong Un continued to conduct missile and nuclear tests, Trump warned the regime of “fire and fury” if it threatened the U.S.. The situation concerned Trump's national security team, including Secretary of State Mike Pompeo, who reportedly said, “We never knew whether it was real” or “a bluff.”

Meanwhile, then-Defense Secretary Mattis, a retired four-star Marine Corps general, had slept in his clothes in case of North Korea's missile launch and visited the nearby Washington National Cathedral to pray, according to CNN's review of the book.

Korea photo

Mattis announced he was resigning from his position in December 2018. He cited disagreements with the president's decision to withdraw U.S. troops from Syria, an unpopular view among senior military leadership and U.S. allies at the time.

“Because you have the right to have a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position,” Mattis wrote in his resignation letter.

For more than a year after his resignation, Mattis, like other retired military leaders, refrained from speaking out against the administration.

In June 2020, however, he penned a statement published in The Atlantic that criticized the administration's controversial response to the Black Lives Matter protests. At the time, people across the country were protesting the Minneapolis police's brutal arrest of George Floyd, prompting the Trump administration to threaten to deploy U.S. combat troops to American cities.

“I have watched this week's unfolding events, angry and appalled,” Mattis said in his statement at the time.

“Donald Trump is the first president in my lifetime who does not try to unite the American people — does not even pretend to try. Instead, he tries to divide us,” Mattis added. “We are witnessing the consequences of three years of this deliberate effort. We are witnessing the consequences of three years without mature leadership.”

Woodward's book adds to Mattis's criticism of Trump, according to CNN. He's quoted as saying the president is “dangerous” and taught the U.S.'s adversaries “how to destroy America.”

Mattis reportedly said he resigned after Trump's move to pullout from Syria, a decision that “basically directed to do something that I thought went beyond stupid to felony stupid.”

Woodward, an award-winning Washington Post journalist known for his work uncovering the Watergate scandal in 1972, has written numerous books about American presidents and their top advisors based on extensive interviews with insiders. He previously published another book about Trump's White House called “Fear: Trump in the White House,” which was sourced from interviews that amassed to “boxes of recordings and documents.”

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