President-elect Joe Biden will become the 46th U.S. commander in chief Jan. 20, U.S. military leaders said in an extraordinary memo to troops.

The said the Jan. 6 attacks on the U.S. Capitol were a "direct assault" on the Constitution.

"As Service Members, we must embody the values and ideals of the Nation," the chiefs said in the memo. "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."

Mark Milley, U.S. Army general and chairperson of the Joint Chiefs of Staff, comprised of the most senior uniformed military leaders, signed the memo along with all seven member of the body that advises the president, secretary of defense and related government agencies on military matters.

"We witnessed actions inside the Capitol building that were inconsistent with the rule of law," said memo said. "The rights of freedom of speech and assembly do not give anyone the right to resort to violence, sedition and insurrection."

Outgoing President Donald Trump faces possible impeachment by the U.S. House of Representatives for allegedly urging protestors to block the counting of Electoral College votes in Congress Jan. 6 - a process that was overseen by vice president Mike Pence in his constitutional role.