NEW YORK (AP) — Former Secretary of Defense Jim Mattis has a book coming out this summer, but he warns that it will not be a “tell-all” about President Donald Trump.

“Call Sign Chaos: Learning to Lead” will be published July 16, Random House announced Tuesday. Co-written with Bing West, the book will be an “expansive account” of the retired general’s military career, according to the publisher. Mattis will write about conflicts from Afghanistan to Iraq and use those experiences for lessons on war and peace. Mattis, a Washington state native, attended events in Seattle over Memorial Day weekend.

The book was under contract before Mattis became defense secretary in early 2017, although it will touch upon events over the past couple of years, a Random House spokesperson told The Associated Press. But “Call Sign Chaos” should be far different in tone from such scathing best-sellers as James Comey’s “A Higher Loyalty” and Michael Wolff’s “Fire and Fury.”

“My purpose in writing this book is to convey some of the lessons I learned in 43 years of service for those who might benefit, whether in the military or in civilian life,” Mattis, 68, said in a statement. “I’m old-fashioned: I don’t write about sitting Presidents, so those looking for a tell-all will be disappointed. I want to pass on the lessons and experiences that prepared me for challenges I could not anticipate, not take up the hot political rhetoric of our day.”

The book’s title comes from Mattis’ call sign, “Chaos,” while he led the 7th Marine Regiment in the mid-1990s. (Trump had favored calling him “Mad Dog,” a nickname Mattis disdained).

Trump initially had high praise for Mattis, a 4-star Marine general who for a time seemed to enjoy a level of respect Trump rarely showed to other cabinet officials. Foreign policy officials viewed him as a stabilizing force within a tumultuous White House and a leading advocate for traditional alliances. But Trump and Mattis would differ on a wide range of issues, from the president’s desire to withdraw troops from Syria to his harsh talk about NATO. Mattis announced late last year he was leaving, writing in his resignation letter that Trump had “the right” to have a defense secretary whose views were aligned with his.

Trump responded by disparaging Mattis’ leadership at the Pentagon and by stating, falsely, that he had “effectively” fired his defense secretary. Mattis has since been virtually silent about his time in the administration.