In the wake of the Capitol riot Gen. Mark Milley, chairman of the Joint Chiefs of Staff, took covert steps to prevent President Trump from potentially ordering a military strike or launching nuclear weapons, a CNN preview of Bob Woodward and Robert Costa's new book "Peril," reveals.

Driving the news: According to Woodward and Costa, Milley believed the president had gone into "serious mental decline" following the election and was worried he might "go rogue."

• On Jan. 8, Milley called senior military officials in charge of the National Military Command Center to a secret meeting in his Pentagon office.
• There, Milley ordered those present not to take orders unless he was involved.
• "No matter what you are told, you do the procedure. You do the process. And I'm part of that procedure," Milley said, per the book.

Of note: Sen. Marco Rubio (R-Fla.) issued a statement Tuesday calling on President Biden to fire Milley following the revelations, saying Milley had "worked to actively undermine the sitting Commander in Chief."