Washington (CNN) President-elect Donald Trump announced Friday three key members of the national security team for his administration -- signaling he will make good on the hard-line agenda on which he campaigned.

Unveiled Friday were nominations of Alabama Sen. Jeff Sessions as attorney general, Kansas Rep. Mike Pompeo as CIA director, and retired Army Lt. Gen. Michael Flynn as national security advisor. Sessions and Pompeo would be subject to Senate confirmation, while the position of national security advisor is not.

All three men take an uncompromising approach to national security and differ sharply from the Obama administration's doctrine. The trio indicate that Trump intends to stand by some of his more controversial national security positions from his campaign, rather than appointing more moderate-leaning candidates.

Sessions is most known for his tough stance on immigration, much like Trump, and backed the Republican presidential nominee's proposal early in the campaign to temporary block all foreign Muslims from entering the US -- a position Trump has since walked back.

Flynn has a reputation for a fiery temperament and has courted controversy with his strident positions on Islam and terrorism, as well as his penchant for sending out conspiracist tweets.

Pompeo, who was not a Trump supporter during the primary, co-authored an "additional views" report to the Benghazi Committee's report on its investigation into the diplomatic mission attack in Benghazi, believing the Republican-led committee's report was not hard enough on former Secretary of State Hillary Clinton and the Obama administration.

Despite Trump's anti-Beltway "drain the swamp" pledge, all three candidates have or have had official positions in Washington. Flynn, who was pushed out of the Defense Department in 2014 , runs a firm that does lobbying. And Sessions and Pompeo come directly from Congress, which has a near-historic low approval rating.

But the trio have also served as thorns in their party's side at times. Flynn was pushed out as director of the Defense Intelligence Agency for his contentious management style, according to US officials, though he says it was because he raised warnings about Islamic terrorism. Sessions was a leader of the opposition to the ill-fated Gang of Eight immigration reform compromise bill negotiated by his more moderate Republican colleagues and Senate Democrats. That bill passed through the Senate, but ultimately died in the House. And Pompeo pushed for more strident findings on the Benghazi Committee, which was already widely criticized by Democrats as being a politically motivated witch hunt against Hillary Clinton.

In fact, Pompeo, Sessions and Flynn have been some of the toughest members of their party on Clinton's use of a private email server, with Flynn leading " lock her up " chants at the Republican National Convention in Cleveland this summer and Sessions criticizing the handling of her investigation by FBI Director James Comey.

As attorney general, Sessions would be ultimately in charge of the prosecutorial decisions made on investigations like the one Comey oversaw on Clinton -- and could clash with the bureau director, who is serving a 10-year term. Trump has pledged to have a special prosecutor investigate Clinton, though he has hedged on whether he will pursue that since being elected.

The move to reinforce Trump's tough campaign rhetoric with his nominees comes as his transition organization has made an effort to portray the President-elect as courting moderates for other positions in the administration -- including publicizing meetings with former critics South Carolina Gov. Nikki Haley and 2012 Republican presidential nominee Mitt Romney, both on the topic of secretary of state. But so far with the exception of GOP Chairman Reince Priebus being named chief of staff, he has drawn from outside the establishment for his Cabinet and advisers.

Hard-line positions

Sessions, Pompeo and Flynn all have taken strong positions on hot-button issues.

Flynn is especially critical of Islamic terror, including a vocal twitter feed on which he has written "fear of Muslims is rational." Sessions also defended Trump when he called for "a total and complete shutdown of Muslims entering the United States" temporarily in the face of terrorism.

Trump has since walked back that position, most recently saying he will pursue a policy similar to after September 11 that requires immigrants from high-risk countries, most of which are Muslim-majority nations, to register in a tracking system.

Flynn has also been criticized for his closeness to Russia, including appearing on a Russian television network and sitting alongside Russian President Vladimir Putin at a dinner celebrating the network, RT. But he has said he didn't take money directly from Russia for his appearance and said he went to tell the Russians to crack down on Iran's involvement in Middle East conflicts.

The willingness to engage with Russia corresponds with Trump's own positions, which drew criticism during the campaign. Trump has repeatedly expressed respect and admiration for Putin, and said he would look to work with Moscow as President.

In addition to his tough position on Clinton's responsibility for the Benghazi attacks, Pompeo has advocated for strengthening the American surveillance apparatus again, calling for the restoration of surveillance powers that were curtailed in bipartisan reforms after the disclosures of Edward Snowden.

"Legal and bureaucratic impediments to surveillance should be removed," he wrote in a Wall Street Journal op-ed.

National security experience

Friday's picks come from a variety of backgrounds and have different levels of experience on issues related to foreign policy, national security and intelligence.

Flynn is a former defense intelligence chief and retired lieutenant general, bringing hefty national security experience to the table. But he has also drawn criticism from within defense community ranks for his management style and for his tendency to espouse positions that are outside of mainstream intelligence and defense thinking.

Sessions, who would oversee both a domestic and national security portfolio at the Justice Department, has a long legal career with experience as his state's attorney general and as a prosecutor. In the Senate he served as a member of the Senate Armed Services Committee.

Pompeo is a graduate of West Point and a veteran of the Army. He has a law degree from Harvard, founded an aerospace company and managed an oilfield service and manufacturing company before joining the House, where he serves on the House Intelligence Committee.

While Pompeo has been active on issues of intelligence, he has no experience from within the actual intelligence community agencies, leaving Flynn as the most experienced member of Trump's team on national security and intelligence. Trump has not yet indicated who he will pick for other key national security posts, including at the Pentagon and to be the Director of National Intelligence.

Flynn will have Trump's ear as his close adviser and will be close to the President-elect in the White House, making it likely that he will have a strong influence over the whole administration's posture.