Army Gen. Mark Milley was 'not going rogue' in secret calls to China, authors of new book claim

Former President Trump's top military adviser was "not going rogue" when he held secret phone calls with his Chinese counterpart before and after the 2020 election, Washington Post reporters Bob Woodward and Robert Costa said on "Good Morning America" Monday.

"He was not going rogue," Costa told ABC News' George Stephanopoulos in an exclusive interview. "He was reading people in throughout the national security community, trying to contain a situation and a president he believed was in serious mental decline."

According to their new book "Peril," which chronicles the end of the Trump administration, Army Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, called Chinese Gen. Li Zuocheng in October 2020 and January 2021 to dispel Chinese fears that Trump was planning a secret attack and to assure him the U.S. was not on the verge of collapse after the Capitol riot.

"If we're going to attack, I'm going to call you ahead of time. It's not going to be a surprise," Milley said on the October call, according to the book.

While Trump and Republicans accused Milley of treason and called on President Joe Biden to fire him amid reports of his phone calls, Costa told Stephanopoulos that Milley was "reading people in" on his conversations, suggesting that their reporting in the book was being misconstrued.

Even though the calls "were held on a top secret back channel, they were not secret," Costa said. "This was not someone who was working in isolation."

Added Woodward: "Two days after the insurrection at the Capitol was a moment of maximum tension."

Speaking to The Associated Press last week in Greece, Milley said the calls were "routine" and done "to reassure both allies and adversaries in this case in order to ensure strategic stability.”

He said he was prepared to defend his actions in testimony before the Senate Armed Services Committee next week.

The new book, which goes on sale Sep. 21, also details how former Vice President Mike Pence grappled with his duties to certify the election results on Jan. 6, as Trump repeatedly pressured him to overturn Biden's victory.

Pence consulted the Senate parliamentarian and former Vice President Dan Quayle on how to approach his ceremonial role presiding over the electoral vote count.

"You don't know the position I'm in," Pence told Quayle.

"I do know the position you're in," Quayle replied, according to the book. "I also know what the law is. You listen to the parliamentarian. That's all you do. You have no power."

Pence, who is eyeing a 2024 White House bid, was "trying to ride both horses," Woodward said. He was trying to "do his constitutional duty but also keep the avenues to Trump open," Woodward added.

Woodward and Costa conducted more than 200 deep background interviews with witnesses or firsthand participants in events described in the book.