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He took the oath of office, gave a fiery speech, moved into the White House, and on Friday night President Donald Trump celebrated at a series of galas, basking in supporters' cheers and promising to get straight to work on a historic transformation of the federal government.

"It’s a movement like they've never seen anytime anywhere in the world," Trump said at the first of three balls he was scheduled to attend with his wife, Melania, and his family. "It’s a movement. And now the work begins."

Related: In Inaugural Address, Trump Pledges to Keep ‘America First’

At the Salute to Our Armed Services Ball, the third and last ball attended by the president Friday evening, Trump was congratulated by soldiers in Afghanistan via live video link and he pledged to them "we’re with you a thousand, a thousand, a thousand percent.”

The crowd roared when Trump announced that retired Gen. James Mattis was sworn in as Defense Secretary Friday. "I have your back. We are going to do great things for our country," Trump said.

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President Donald Trump dances with first lady Melania Trump, at The Salute To Our Armed Services Inaugural Ball in Washington, Friday, Jan. 20, 2017. Evan Vucci / AP

At the first ball of the evening, Trump, in a tuxedo, opened his remarks by reminding his audience of his darkhorse victory, and how his detractors were now eating crow. He described the rain that began after his inaugural address, which left him feeling "like God was looking down on us."

And Trump predicted that he was going to get started immediately on enacting his agenda.

"You’re going to see things happen over the next few weeks, oh, you’re going to be so happy," he told the crowd.

A few hours earlier, Trump took his first official action as president, signing an executive order to "minimize the economic burden" of Obamacare until it can be repealed.

Related: Trump Signs Executive Order on Obamacare on Inauguration Day

Trump also signed commissions for retired Mattis as Defense Secretary and Gen. John Kelly to run the Department of Homeland Security, after both were easily confirmed by the Senate.

After his remarks at the first ball, Trump and his wife danced to the song "My Way," a song he often cited on the campaign trail.

Then they went straight to a second party, where Trump worked the crowd a bit more, asking if he should keep tweeting (the people roared its approval).

"The enemies keep saying that's terrible, but it's a way of bypassing dishonest media," Trump said.

He made circles with his hand. "You go wah, wah."

Trump shared the news about Mattis and Kelly. "So we're starting to work," he said. "We are not going to let you down. Remember the theme. Make America great again."