• Secretary of the Army Ryan McCarthy said that the intelligence law and Defense officials had prior to the riot at the U.S. Capitol "was all over the board."
• Through the weekend, 6,200 National Guard personnel will deploy to the nation's capital and remain in the region for a minimum of 30 days.
• The troops, who are unarmed, will monitor traffic control points and provide support to law enforcement.

WASHINGTON — Secretary of the Army Ryan McCarthy said Thursday that the intelligence law and Defense officials had prior to the riot that rocked Washington "was all over the board."

"There were estimates of 80,000 there were estimates around 20 to 25. So getting back to just the pure intelligence. It was all over the board," McCarthy explained when asked about preparations for crowd control.

"It was very hard to make that determination of what you're dealing with," he told reporters on a call, adding that the Defense department relied on law enforcement threat assessments.

Through the weekend, 6,200 National Guard personnel will deploy to the nation's capital and remain in the region for a minimum of 30 days. The month-long mobilization ensures that the National Guard members will be on hand for the Jan. 20 inauguration of President-elect Joe Biden.

The troops, who are unarmed, will monitor traffic control points and provide support to law enforcement as authorities work to secure the perimeter surrounding the Capitol Building one day after a mob supporting President Donald Trump stormed it.

The mobilization comes as the nation continues to process Wednesday's startling riot in which at least four people died. All four living former presidents have condemned the day's events, in which a violent mob disrupted lawmakers from the typically perfunctory process of formally confirming Biden's victory.

The D.C. National Guard was mobilized during the riots and about 1,100 troops were sent to assist local police in tamping down the insurrection, the Pentagon said. The deployment came after Washington, D.C., Mayor Muriel Bowser and House Speaker Nancy Pelosi requested the force, two sources told NBC News.

Virginia Gov. Ralph Northam, Maryland Gov. Larry Hogan and New York Gov. Andrew Cuomo all announced plans to send National Guard troops to D.C. as well.

Trump, who spoke at a rally to protest the results of the election shortly before his supporters infiltrated Congress, still has not condemned the rioting or conceded defeat.

He encouraged demonstrators to be peaceful after they stormed the Capitol.

The president has continued to assert baseless allegations of voter fraud, in spite of the findings of his own administration's departments of Justice and Homeland Security to the contrary.

It is typical for the National Guard to be present for inaugurations, and more than 7,000 troops were mobilized for Trump's inauguration in 2017.

Biden's inauguration is expected to look very different from previous ceremonies as a result of public health precautions.

Biden and Vice President-elect Kamala Harris will take their oaths of office at the Capitol on Jan. 20, but otherwise have altered the tradition to adapt to the spreading coronavirus pandemic.

The Biden transition team has said it is reimagining the typical gathering on the National Mall and the inaugural parade from the Capitol to the White House in a way that will allow Americans to participate from home.

Biden condemned the rioting on Wednesday in a nationally televised address.

"At this hour, our democracy is under unprecedented assault," the former vice president said.

"It's chaos, it borders on sedition, and it must end now. I call this mob to pull back and allow this work of democracy to go forward," Biden added.

The success the rioters had in breaking through police barriers has raised questions about the security precautions that will be in place for the inauguration.

Sen. Amy Klobuchar, D-Minn., who is on the committee planning Biden's inauguration, said on CBS News that "there's going to have to be major, major reviews of what happened and changes made."

Klobuchar added that, compared to the counting of Electoral College votes, which generally takes place without incident, the inauguration is a major security event every four years.

"Here they had an event that usually goes along with little historical note," Klobuchar said.

CNBC's Tucker Higgins reported from New York.

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