A close adviser to Richland's James Mattis is writing a book on the former defense secretary’s “complicated relationship” with President Donald Trump.

“Holding the Line: Inside the Pentagon With General Mattis” is written by the secretary’s former communications director, retired Navy Cmdr. Guy “Bus” Snodgrass, and is expected to be released in October.

A press release for the book promises “an insider's sometimes shocking account of how [Mattis] led the U.S. military through global challenges while serving as a crucial check on the Trump Administration.”

"Holding the Line" is the first book by one of Mattis' closest advisers, and is the first look behind the scenes of Mattis' nearly two-year tenure as defense secretary. Mattis, a former Marine Corps general, rarely engaged with the media and kept a lower profile than previous defense secretaries. Mattis resigned in December 2018 after President Trump announced an immediate U.S. withdrawal from Syria.

Snodgrass is a former F/A-18 fighter pilot for the Navy who took meticulous notes during his 17 month tenure with Mattis, attending critical national security events and crises, including witnessing the defense secretary "learning about major policy decisions via Twitter, rather than from the White House."

The author's goal is to provide a "fly-on-the-wall" review of Mattis navigating his way through the Trump administration and how he "slow-rolled some of President Trumps' most controversial measures, with no intention of following through."

The book promises to be full of "never-before-told stories that will both alarm and reassure, a testament to the quiet and steady efforts of General Mattis and the dedicated men and women he led at the Department of Defense."

When completed, the book must be submitted to the Pentagon for review before publication to ensure no classified material is inadvertently included.