Sneak peek: Robert Gates' new book discusses serving 8 presidents

Former Defense Secretary Robert Gates — who played the unusual role of bridging the Bush and Obama administrations, and served eight presidents of both parties — is out Tuesday with "Exercise of Power: American Failures, Successes, and a New Path Forward in the Post-Cold War World" (Knopf).

The big picture: Gates argues that the U.S. should have withdrawn from Afghanistan in 2002, cyber has become the most powerful weapon in a nation's arsenal, and North Korea has no intention of ever giving up its nuclear weapons.

Why "Exercise of Power" matters, from Gates' prologue:

There are many studies and books on how the United States has applied its power since 1993 and should apply it in the future. Few of those authors, however, have actually had power and exercised it; only a handful have been firsthand witnesses to history making, and then nearly always under just one or two presidents.

The authors are mostly foreign policy mavens, historians, and political scientists who write from think tanks, universities, institutes, and other such perches. ...

I witnessed and participated in decision making under more presidents of both parties than any other contemporary senior official.