Former Defense Secretary Jim Mattis doesn’t recite any of his conversations with President Trump in his upcoming book (much to the consternation of Washington journalists). But he does detail an evening with someone else who might be on the presidential ballot in 2020: Joe Biden, who was “ignoring reality” in Iraq, he says.

In Call Sign Chaos: Learning to Lead, co-written with Bing West and set to be published Tuesday, Mattis expounds on the lessons learned in his more than 40 years in the Marine Corps. His career culminated in three years as the head of U.S. Central Command, overseeing military operations in the Middle East and Central Asia from 2010 to 2013. That meant Mattis was in charge of American troops in Iraq and Afghanistan as war raged in both countries.

Mattis served under President Obama, and Vice President Biden visited Baghdad in the late summer of 2010. The general writes that the U.S.-led coalition had “at last succeeded in establishing a fragile stability” in Iraq. The administration was considering withdrawing some troops, and any forces remaining would require the permission of the Iraqi government, then led by the embattled Nouri al-Maliki. “The National Security staff in the White House believed that Maliki offered a continuity that, in their minds, would facilitate the withdrawal of U.S. troops.” Mattis disagreed, and he told Biden so during dinner after “a hot Baghdad day.”

“Prime Minister Maliki is highly untrustworthy, Mr. Vice President,” Mattis said. “He’s devious when he talks to us.”

Mattis noted that in the election that year, Maliki had not garnered a majority of the votes, and he seemed to be stonewalling the formation of a new government. The Shiite leader had cultivated relationships with officials in Iran and Syria in the years he spent plotting to overthrow Saddam Hussein.

“He looks at our ambassadors and military advisers as impediments to his anti-Sunni agenda,” Mattis told Biden, who was leading the administration's Iraq policy. “He wants to purge or marginalize Sunnis and Kurds from the government.” Mattis said leaders across the Middle East had warned against continuing to throw American support behind Maliki.

Mattis also argued against pulling out precipitately. He said the training wheels shouldn’t suddenly be pulled off the bicycle. “We should slowly inch the wheels up, allowing the Iraqis to wobble but not crash as they slowly pedaled down the path to self-sufficiency,” he said. “If we pulled out too early, I noted, we would have to bring our troops back in.”

The general’s assessment fell on deaf ears.

“Vice President Biden and his assistants listened politely. But as we spoke, I sensed I was making no headway in convincing the administration officials not to support Maliki. It was like talking to people who lived in wooden houses but saw no need for a fire department,” Mattis writes.

“I liked the Vice President,” Mattis writes, even after Biden teased him: “Know why you’re at CENTCOM?” Biden asked him. “Because no one else was dumb enough to take the job.”

“I found him an admirable and amiable man. But he was past the point where he was willing to entertain a ‘good idea.’ He didn’t want to hear more; he wanted our forces out of Iraq. Whatever path led there fastest, he favored,” Mattis writes. “He exuded the confidence of a man whose mind was made up, perhaps even indifferent to considering the consequences were he judging the situation incorrectly.”

Biden reassured Mattis that Maliki wouldn’t eject all American troops from the country.

“Maliki wants us to stick around, because he does not see a future in Iraq otherwise,” Biden said. “I’ll bet you my vice presidency.”

Mattis doesn’t say whether he tried to collect on that bet. As he writes, “In October 2011, Prime Minister Maliki and President Obama agreed that all U.S. forces would leave at the end of the year.”

Mattis’ warnings proved prescient, as Maliki, free of American influence, went after Sunni politicians and districts, alienating a third of the country. “Iraq slipped back into escalating violence. It was like watching a car wreck in slow motion,” Mattis writes. A Sunni revolt and a weak Iraqi Army allowed al Qaeda-aligned terrorists to return in 2014, calling themselves the Islamic State.

“It would take many years and tens of thousands of casualties, plus untold misery for millions of innocents, to break ISIS’s geographic hold,” Mattis writes. “All of this was predicted — and preventable.”

Biden has been touting on the campaign trail his role in the decision that Mattis believes, as do many other experts, led to the rise of ISIS. “I was responsible for getting 150,000 combat troops out of Iraq — my son was one of them,” he said on the Democratic debate stage in June.