Chairman of the Joint Chiefs of Staff, U.S. Army Gen. Mark A. Milley, answers a question during a virtual town hall at the Pentagon, May 28, 2020.

Chad J. McNeeley | Department of Defense

WASHINGTON — In an extraordinary letter Tuesday to the U.S. military, the nation's top commanders condemned last week's acts of "sedition and insurrection" at the U.S. Capitol, while acknowledging Joe Biden's election victory.

The message did not mention President Donald Trump by name, but the Joint Chiefs of Staff, led by U.S. Army Gen. Mark Milley, made it clear that the military intends to stand by the constitutional transfer of power to the next administration.

"As we have done throughout our history, the U.S. military will obey lawful orders from civilian leadership, support civilian authorities to protect lives and property, ensure public safety in accordance with the law, and remain fully committed to protecting and defending the Constitution of the United States against all enemies, foreign and domestic," wrote the nation's highest military officers.

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"As Service Members, we must embody the values and ideals of the Nation. We support and defend the Constitution. Any act to disrupt the Constitutional process is not only against our traditions, values and oath; it is against the law," the chiefs wrote.

The message to the troops comes nearly one week after thousands of the president's supporters stormed the U.S. Capitol, resulting in at least five deaths, including that of a Capitol Police officer.

Earlier on Tuesday, Trump told reporters that people found his comments at a rally that sparked the violence at the Capitol "totally appropriate" and called the fallout "absolutely ridiculous."

The president also briefly discussed the blowback he said would follow potential impeachment proceedings.

"For [House Speaker] Nancy Pelosi and [Senate Democratic leader] Chuck Schumer to continue on this path, I think it's causing tremendous danger to our country, and it's causing tremendous anger," he said.

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On Wednesday, the House plans to decide whether to make Trump the first president ever impeached twice.

The assault on the Capitol delayed congressional proceedings to tally electors' votes and confirm Biden's win in the Nov. 3 election.

Biden's victory was projected by all major news outlets in mid-November and confirmed by Electoral College votes in mid-December. The Republican president has falsely insisted he won in a "landslide," baselessly claiming his reelection was stolen through massive electoral fraud.

As protesters besieged the Capitol on Wednesday, Trump told supporters in a tweeted video, "You have to go home now." The president stopped short of condemning the violence and told the mob, "We love you, you're very special."

US President Donald Trump looks on after presenting the Presidential Medal of Freedom to Celtics basketball legend Bob Cousy in the Oval Office of the White House in Washington, DC on August 22, 2019.

Mandel Ngan | AFP | Getty Images

On Monday, Sen. Tammy Duckworth, D-Ill., called on acting Defense Secretary Chris Miller to investigate whether active-duty or retired military members took part in the deadly mob.

If such individuals are identified by criminal investigators, Duckworth said, Miller must "take appropriate action to hold individuals accountable under the Uniform Code of Military Justice." Duckworth, an Iraq War veteran who retired as a lieutenant colonel from the Army National Guard, noted that "upholding good order and discipline demands that the U.S. Armed Forces root out extremists that infiltrate the military and threaten our national security."

A U.S. Army officer resigned Monday after commanders at Fort Bragg confirmed that they were reviewing Capt. Emily Rainey's involvement in the riot.

In a Tuesday evening statement, the Army said it is working with the FBI to determine whether any participants in last week's riot have any connection to the Army.

"Any type of activity that involves violence, civil disobedience, or a breach of peace may be punishable under the Uniform Code of Military Justice or under state or federal law," an Army spokesperson wrote in an emailed statement.

In a nearly three-minute video posted on Thursday, the president called for national "healing and reconciliation."

"To those who engaged in the acts of violence and destruction, you do not represent our country. And to those who broke the law, you will pay," Trump said, in his first address to the nation following the violence that rocked Washington.

"Now tempers must be cooled, and calm restored. We must get on with the business of America," Trump added.

The president also acknowledged that "a new administration will be inaugurated on Jan. 20."

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A day later he said that he would skip President-elect Joe Biden's inauguration. Vice President Mike Pence said he will attend Biden's swearing-in ceremony.

Traditionally, the incoming and outgoing presidents ride from the White House to the U.S. Capitol together for the inauguration ceremony.

Trump is not the first outgoing president to skip the inauguration of his successor. The others were Presidents John Adams, John Quincy Adams and Andrew Johnson, according to the White House Historical Association. Like Trump, Johnson was also impeached.

The National Guard said Monday that it has authorized up to 15,000 troops to support the security of the inauguration. Defense officials added that there were approximately 9,000 National Guard members at former President Barack Obama's inauguration. For Trump's ceremony in 2017, more than 7,000 troops were mobilized.

Top military leaders condemn 'sedition and insurrection' at Capitol, acknowledge Biden win