Updated

As President Trump announces a major shakeup of his National Security Council, there is a growing focus on what exactly the NSC does and what the impact of this rearrangement could be.

Lt Gen H.R. McMaster has served as the President's National Security Advisor since February, but it was the removal of one of the president's closest aides, Steven Bannon, from the National Security Council's Principals Committee that is drawing the most attention.

The Principals Committee is made up of people who are considered the President's top national security officials, and is tasked with a variety of issues that affect our national security. In a new White House memo that lists the committee’s members, Bannon is not mentioned.

According to the memo, the Principals Committee is now comprised of "the Secretary of State, the Secretary of the Treasury, the Secretary of Defense, the Attorney General, the Secretary of Energy, the Secretary of Homeland Security, the Chief of Staff to the President, the Director of National Intelligence, the Chairman of the Joint Chiefs of Staff, the Director of the Central Intelligence Agency, the National Security Advisor, the Homeland Security Advisor, and the Representative of the United States to the United Nations."

In addition to those members, the memo states that "[t]he Counsel to the President, the Deputy Counsel to the President for National Security Affairs, and the Director of the Office of Management and Budget may attend all [Principals Committee] meetings."

In a statement, Bannon suggested that President Obama's National Security Adviser, Susan Rice, had "operationalized the [National Security Council] during the last administration," adding that he was only ever put on to "ensure that it was de-operationalized."

Bannon added that he believes McMaster "has returned the NSC to its proper function."

A senior administration official tells Fox that Bannon was only ever put on the committee as a check on former National Security Advisor, Lt Gen Michael Flynn. According to the official, the President saw no need for Bannon to stay on after McMaster assumed the role of advisor, but suggested that Bannon will still be able to attend NSC meetings.

Bannon’s initial placement on the NSC created controversy among both Republicans and Democrats, who suggested that Bannon could wind up inserting domestic politics into discussions of national security. Press Secretary Sean Spicer said in February that the President would be willing to reconsider Bannon’s role on the NSC if McMaster asked.

The National Security Council was created in July, 1947, as part of President Truman's National Security Act. According to the Nixon Presidential Library, the NSC was created "to assist and advise the President on domestic, foreign and military policies relating to national security." At the time, the council consisted of just seven permanent members, with the President serving as chairman.

Just a few years later, the NSC went through a reorganization that placed the NSC within the executive office of the President. A series of amendments resulted in the council being divided into three groups: the Executive Secretary and his staff, personnel on detail, and Consultants to the Executive Secretary.

Former National Security Advisor Brent Scowcroft pointed out in an interview with the Council on Foreign Relations that the size of the NSC has "varied dramatically from the minimum, which was five people under Kennedy, with virtually no staff, to what it is now, which I think is about 350."

According to a Congressional Research Service report on the NSC, the group’s organization and even influencehave varied significantly from one Administration to another, ranging from highly structured and formal systems to loose-knit teams of experts.”

Today, the council's members include (by statute) the president, the vice president, and the secretaries of state, defense and energy. The chairman of the Joint Chiefs of Staff and the Director of National Intelligence are said to serve in advisory roles, and the president has the discretion to add other members as they see fit.

At the time of publishing Wednesday afternoon, visitors to the NSC's White House website were being told to “[c]heck back soon for more information.”