AMNA NAWAZ: President Donald Trump will hit his first 100 days in the White House on Tuesday, a key period of his second presidency, defined by its breakneck pace and the chaotic rollout of an agenda designed to expand his authority.

Laura Barron-Lopez has our report.

DONALD TRUMP, President of the United States: So this is a big one.

LAURA BARRON-LOPEZ: Since retaking the Oval Office in January, Donald Trump has tested the limits of presidential power.

DONALD TRUMP: We have rogue judges that are destroying our country.

LAURA BARRON-LOPEZ: More than 140 executive orders signed, a record for the first 100 days, and tariffs on allies and adversaries alike, a growing deportation operation, and mass firings across the government, all at a pace that historian Mark Updegrove says has institutions struggling to keep up.

MARK UPDEGROVE, Presidential Historian: There's a muzzle velocity, this flooding the zone of activity that has come since he took the Oval Office.

There have been enormous gambles that he has taken.

And we don't yet know what the ramifications of those gambles are.

LAURA BARRON-LOPEZ: Impulsive and often controversial, just one month in, President Trump shocked the world... DONALD TRUMP: You don't have the cards right now.

LAURA BARRON-LOPEZ: ... when he berated Ukrainian President Volodymyr Zelenskyy in an explosive Oval Office showdown that forced allies to reckon with what could be the end of the transatlantic alliance.

DONALD TRUMP: You're gambling with World War III.

And what you're doing is very disrespectful to the country, this country... VOLODYMYR ZELENSKYY, Ukrainian President: I'm with all respect to you.

DONALD TRUMP: ... that's backed to you far more than a lot of people said they should have.

J.D.

VANCE, Vice President of the United States: Have you said thank you once this entire meeting?

VOLODYMYR ZELENSKYY: A lot of times.

J.D.

VANCE: No, in this entire meeting, have you said thank you?

LAURA BARRON-LOPEZ: And now the administration is threatening to walk away from the peace negotiations.

On immigration, Trump moved quickly to shut down the border in many legal pathways to enter the U.S., southern border crossings dropping to the lowest levels in decades, carrying out early raids in major cities.

Top immigration officials launched a P.R.

blitz to highlight the deportations and pressure immigrants to self-deport.

KRISTI NOEM, U.S.

Homeland Security Secretary: If you are considering entering America illegally, don't even think about it.

LAURA BARRON-LOPEZ: College students were also targeted in the dragnet, as the administration revoked visas from hundreds of foreign students involved in pro-Palestinian campus protests and has detained a growing number of legal permanent residents.

The targeting of undocumented and legal immigrants alike has set off a confrontation with coequal judicial branch.

After invoking the 18th century Alien Enemies Act, until now only used during times of war, the administration deported hundreds of Venezuelan migrants alleged to be gang members without due process.

DONALD TRUMP: These were bad people.

That was a bad group of, as I say, hombres.

LAURA BARRON-LOPEZ: A move that federal judges, including Republican-appointed ones, have described in rulings as shocking and a path of perfect lawlessness, one that courts cannot condone.

In an extraordinary response, the Supreme Court halted all future deportations under the Alien Enemies Act until courts can hear more arguments.

And they ordered the administration to -- quote -- "facilitate" the return of Kilmar Abrego Garcia, who was illegally deported to El Salvador, despite a court order expressly forbidding him to be sent there.

The White House taunting on social media that Garcia is never coming back.

MARK UPDEGROVE: Donald Trump has shown that he has disregarded at certain points of his presidency constitutional and conventional norms.

Will there be a continued defiance of court orders and what will that mean to our Constitution?

What will that mean to the future of America?

ELON MUSK, Department of Government Efficiency: Do you have a pulse?

LAURA BARRON-LOPEZ: Acting with Trump's blessing, special government employee Elon Musk has exerted unprecedented influence inside the administration, while vowing to take a chain saw to the federal government.

He's promoted Teslas on the White House driveway.

ELON MUSK: It's zero to 60 miles an hour in two seconds.

LAURA BARRON-LOPEZ: Musk's so-called Department of Government Efficiency, or DOGE, claims to have cut $160 billion in spending since Trump took office, nowhere near the $1 trillion promised by September.

ELON MUSK: Some of the things that I say will be incorrect and should be corrected.

So nobody's going to bet .1000.

We will make mistakes.

LAURA BARRON-LOPEZ: And many of DOGE's -- quote -- "receipts" have been riddled with billion-dollar errors, deletions or falsehoods.

DONALD TRUMP: When you look at the kind of money, billions and billions of dollars being thrown away illegally.

LAURA BARRON-LOPEZ: At the direction of Musk and his allies across the government, nearly 280,000 federal workers have been fired or put on leave.

Most foreign aid spending has been eliminated, including the dismantling of the U.S. Agency for International Development, known as USAID.

And there have been major cuts at the Department of Education, the Environmental Protection Agency and others, like the Centers for Disease Control and Prevention.

MARK UPDEGROVE: We have never seen the dismantling of government to this extent.

These programs are baked into American life.

And it's everything from the CDC to the FAA and to all these different things that we almost take for granted in our daily lives as Americans.

And we have never seen an axe wielded to take apart government to this extent.

DONALD TRUMP: My fellow Americans, this is liberation day.

LAURA BARRON-LOPEZ: And after promising to rein in inflation and lower the price of goods, President Trump unveiled sweeping tariffs on nearly all of the nations that trade with the U.S., before he backtracked, announcing a 90-day pause just hours before they were set to take effect.

DONALD TRUMP: Well, I thought that people were jumping a little bit out of line.

They were getting yippy, you know?

They were getting a little bit yippy, a little bit afraid.

LAURA BARRON-LOPEZ: Still, Trump left in place an across-the-board 10 percent tariff on most imported goods and 25 percent levies on foreign autos, steel and aluminum.

And he launched a bitter trade war with China, slapping 145 percent tariffs on most Chinese products imported to the U.S., prompting China to retaliate, all sparking chaos in the financial markets and, according to a majority of economists, raising the risk of recession.

MARK UPDEGROVE: We have not seen tariffs used as a weapon in the manner that Trump has used them to this point.

While this might seem like a good short-term solution to get nations to the bargaining table to get better deals from America, the long-term downstream effects of this remain to be seen, and it's an enormous gamble for America and for the world economy.

DONALD TRUMP: They weaponized the vast powers of our intelligence and law enforcement agencies to try and thwart the will of the American people.

LAURA BARRON-LOPEZ: And despite railing against what he called the weaponization of government against him, many say President Trump has made good on his promise of retribution, attacking all perceived enemies, stripping security clearances from former officials in his first administration and other political opponents, including Republicans, threatening law firms that worked on legal cases against him, punishing independent news organizations he disagrees with, and targeting institutions like Harvard University by halting billions in public funding.

Are there historical parallels?

Are there other presidents who attempted to go after their enemies in the same way that Trump is going after his?

MARK UPDEGROVE: Not to the same extent that we have seen from Donald Trump, no.

We saw from Richard Nixon attacks on his enemies.

He had an enemy list, but they were not -- that vengeance was not carried out to the same systematic degree that we have seen from the Trump administration.

LAURA BARRON-LOPEZ: President Trump has made clear he will move to enact his agenda with or without Congress.

But the near-daily court setbacks continue, as the judiciary questions the legality of some of his actions.

MARK UPDEGROVE: Donald Trump campaigned on the notion of making America great again.

We have seen him tear down much of what has made America great to this point.

What will he build in its place and where will its greatness lie?

DONALD TRUMP: Thank you, everybody.

LAURA BARRON-LOPEZ: Whether the chaos of the president's first 100 days becomes a hallmark of his second term, Updegrove said, remains to be seen.

For the "PBS News Hour," I'm Laura Barron-Lopez.