He is mum on Trump but skewers Obama for taking a wrecking ball to American prestige and power.

Most of the coverage of James Mattis’s new book, Call Sign Chaos, co-authored with Bing West, deals with the former defense secretary’s relationship with President Trump. The Atlantic‘s pre-publication interview with Mattis was headlined, “The Man Who Couldn’t Take It Anymore.” The New York Times editorial page ran a column about Mattis called “The Man Trump Wishes He Were.

Both articles establish that Mattis doesn’t have much to say right now, in either the book or in interviews, about President Trump. Neither piece, though, mentions another president about whom Mattis is more than willing to dish. That would be Barack Obama, who was Mattis’s commander in chief when the then–Marine general led Central Command. Mattis’s critique of Obama isn’t just harsh. It’s blistering.

Mattis’s tenure at Central Command lasted from 2010 to 2013. It was during this time that the Obama administration took steps that diminished American influence in the greater Middle East and empowered Iran. The spillover effect includes the migrant crisis that contributed to the rise of national populism in Europe. Mattis dissented from Obama policy. “In 2010,” he writes, “I argued strongly against pulling all our troops out of Iraq.”