Washington CNN  — 

The defense of the top US military official kicked into gear across Washington Wednesday in response to claims that Gen. Mark Milley overstepped his authority during the waning days of the Trump administration.

The Joint Chiefs chairman came under attack Tuesday over new reporting in “Peril,” a forthcoming book by Washington Post reporters Bob Woodward and Robert Costa, which details Milley’s phone conversations to reassure a nervous Chinese general and efforts Milley took to limit then-President Donald Trump from potentially ordering a dangerous military strike.

Milley’s actions, which were reported by CNN and others on Tuesday ahead of the book’s release next week, spawned sharp criticism of Milley from Trump and his allies, including calls for his resignation and that he be tried for treason.

In response, the White House issued full-throated support for Milley on Wednesday. White House press secretary Jen Psaki called him “a man of honor,” and President Joe Biden said, “I have great confidence in General Milley.”

Former Trump national security adviser John Bolton, who worked alongside Milley in the Trump administration, also spoke out in Milley’s defense, and Milley’s spokesman released a statement asserting that Milley had acted propenrly.

Current and former defense officials pushed back Wednesday on the notion that Milley was out of line, saying his calls to his Chinese counterpart were conducted under protocols similar to other high-level engagements by the Joint Chiefs chairman and in consultation with civilians at the Defense Department, implicitly rejecting criticism that Milley acted in secret.

There were 15 people on both videoconference calls Milley held with his Chinese counterpart, one on October 30 and another on January 8 – including a representative from the State Department, according to one defense official. The read-out and notes from the calls were shared with the intelligence community and the interagency, the official said.

Two backchannel calls

The upcoming book “Peril” documents the two backchannel calls Milley placed to China’s top general, Li Zuocheng, which Milley initiated due to intelligence suggesting China believed the US was going to attack them. Milley sought to calm Li by reassuring him that the US was not considering a strike.

“General Li, you and I have known each other for now five years. If we’re going to attack, I’m going to call you ahead of time. It’s not going to be a surprise. It’s not going to be a bolt out of the blue,” Milley said in the October 30 call, according to Woodward and Costa.

“If there was a war or some kind of kinetic action between the United States and China, there’s going to be a buildup, just like there has been always in history,” he told Li according to the book.

Joint Chiefs Chairman Gen. Mark Milley, top center, watches as President Donald Trump signs the National Defense Authorization Act for Fiscal Year 2020 at Andrews Air Force Base, Maryland, December 2019.

“Peril” also details a secret meeting Milley convened in his office at the Pentagon two days after the January 6 attack at the Capitol, in which Milley went over the procedure for launching nuclear weapons, telling top military officers they needed to consult him before proceeding with any order. “No matter what you are told, you do the procedure. You do the process. And I’m part of that procedure,” Milley said, according to the book.

Milley conducted the October 30 call in consultation with then-Defense Secretary Mark Esper. But former acting Defense Secretary Chris Miller told CNN on Wednesday he wasn’t told the extent of Milley’s engagement with the Chinese.

“Thinking back, I suspect Milley provided me a perfunctory ‘I’m calling my foreign counterparts to check in’ after 1/6 during our daily ‘stand up’ sync/coordination meeting,” Miller told CNN in a text. “But it certainly wasn’t an in-depth convo and definitely no details about themes and content.”

According to the book, Milley reassured Li during that second call that while the United States might appear “unsteady” after the Capitol attack, “We are 100 percent steady. Everything is fine.”

“I wouldn’t have approved of anything of the nature portrayed in Woodward’s book,” Miller said.

A defense official familiar with the call said Miller’s office was appropriately informed.

Milley’s spokesman, Col. Dave Butler, said in a statement that Milley’s calls with other chiefs of defense “remain vital to improving mutual understanding of US national security interests, reducing tensions, providing clarity and avoiding unintended consequences or conflict.”

“His calls with the Chinese and others in October and January were in keeping with these duties and responsibilities conveying reassurance in order to maintain strategic stability,” Butler said. “All calls from the Chairman to his counterparts, including those reported, are staffed, coordinated and communicated with the Department of Defense and the interagency.”

GOP attacks Milley

But the revelation of the two calls quickly garnered criticism from some former Trump administration officials and Republican lawmakers, who have characterized it as dangerous freelance diplomacy done behind closed doors. It wasn’t necessarily the calls themselves that alarmed Milley’s critics, but the assurances he offered to China that the US wouldn’t launch a surprise attack.

Hours after reports from CNN and the Washington Post published with the new details from “Peril,” Florida GOP Sen. Marco Rubio called on President Joe Biden to fire Milley.

Milley “worked to actively undermine the sitting Commander in Chief of the United States Armed Forces and contemplated a treasonous leak of classified information to the Chinese Communist Party in advance of a potential armed conflict with the People’s Republic of China,” Rubio wrote in a letter to Biden Tuesday.

Rubio charged that Milley’s instruction to officers to call him before carrying out any orders had “interfered with the procedures by which the civilian commander-in-chief can order a nuclear strike.”

Sen. Ted Cruz, a Texas Republican, told reporters Tuesday that Milley had to address whether the quotes attributed to him in the book were true. “If they are, that is a gross violation of the chain of command,” Cruz said. “Our constitution embeds a civilian control of the military, and if the chairman of the joint chiefs was actively undermining the commander in chief and pledging to our enemies to defy his orders, that is completely inconsistent with his responsibilities.”

Cruz added that he “hoped the quotes are inaccurate.”

And Trump issued a statement of his own Tuesday evening suggesting that Milley should be tried for treason, adding that he had “never even thought of attacking China.”

Pentagon press secretary John Kirby said Milley’s actions were “completely appropriate” to review the protocols for launching nuclear weapons, and that as the key military adviser to the president, Milley would be “intimately involved” in any decision to launch nuclear weapons.

The scrutiny of Milley comes after some Republicans last month demanded Milley and other top Biden national security officials resign following the missteps of the US withdrawal from Afghanistan last month.

Milley to testify later this month

Milley is sure to face sharp questions publicly about his actions in the final days of the Trump administration when he’s scheduled to testify before the Senate Armed Services Committee on September 28.

Still, a GOP congressional aide said most Republicans were likely to want to keep focused on the US withdrawal from Afghanistan at the hearing, which will be the first time Milley and Defense Secretary Lloyd Austin testify on the withdrawal.

Some former officials came to Milley’s defense.

“In the days after Donald Trump’s November 3, 2020, election defeat, I can only imagine the pressures he and others were under in fulfilling their Constitutional obligations,” Bolton said in a statement. “I have no doubt General Milley consulted widely with his colleagues on the National Security Council and others during this period. I would also be very surprised if many of them were not fully aware of General Milley’s actions, and that they fully concurred in them.”

In “Peril,” Woodward and Costa write that Milley placed the call to his Chinese counterpart on October 30 when “sensitive intelligence” showed that the Chinese “thought that Trump in desperation would create a crisis, present himself as the savior and use the gambit to win reelection.”

A former senior defense official told CNN that the Chinese were unusually concerned about the rhetoric coming out of Washington in the days before the election, and the public rhetoric on the Chinese side was escalating as a result. Esper tasked his top policy official with getting a backchannel message to Beijing to reassure the Chinese, which was done before Milley’s call, the former official said.

“It was a two-step process led by the SecDef and DoD civilians,” the official said. “That’s an important distinction. The purpose was to avoid any unnecessary confrontation that could lead to conflict.”

The second call Milley made was placed was on January 8, and Woodward and Costa write that Milley knew Chinese leadership were “stunned and disoriented by the televised images of the unprecedented attack on the American legislature.” Other countries, including Russia and Iran, were also on high alert.

“Things may look unsteady,” Milley said on the call, according to the book. “But that’s the nature of democracy, General Li. We are 100 percent steady. Everything is fine. But democracy can be sloppy sometimes.”

After the call, Milley “was convinced the situation was grave,” according to the book, as Li remained unusually rattled.

Later that day, House Speaker Nancy Pelosi called him, pressing Milley about how Trump could be stopped from using nuclear weapons. Milley reassured Pelosi on the call, according to a transcript of the conversation detailed in “Peril.” But after that second call, Milley decided to convene the meeting in his office, according to the book, where he told officers to consult him before carrying out orders for a military strike or to launch nuclear weapons.

CNN’s Jamie Gangel, Elizabeth Stuart and Oren Liebermann contributed to this report.