WASHINGTON (AP) — Former Defense Secretary Jim Mattis warns bitter political divisions have pushed American society to the "breaking point" in his most extensive public remarks since he resigned in protest from the Trump administration.

Mattis also goes into some reasons he left the Trump administration in an excerpt from his book published Wednesday by The Wall Street Journal.

The retired Marine general writes he quit in 2018 when he realized his advice to President Donald Trump "no longer resonated" particularly with regard to "keeping faith" with allies.

Mattis resigned shortly after Trump announced he was pulling all U.S. troops from Syria. In Mattis' view this amounted to betraying the Syrian Kurdish fighters who'd partnered with American troops to combat the Islamic State group.

The essay was adapted from Mattis' book, "Call Sign Chaos: Learning to Lead," being published Sept. 3.