Biden strikes a contrast with Trump, offering a choice between ‘revenge’ and ‘decency.’

President Biden used his State of the Union address on Thursday to launch a series of fiery attacks against former President Donald Trump, a competitor whom he did not mention by name but made clear was a dire threat to American democracy and stability in the world.

In a televised speech to a joint session of Congress, Mr. Biden brought the energy his allies and aides had hoped he would display to warn of what could happen should Ukraine continue to lose ground to Russia. Invoking an overseas war at the top of his address was an unusual introduction to a speech that was in many ways a political argument for his re-election.

“Not since President Lincoln and the Civil War have freedom and democracy been under assault at home as they are today,” Mr. Biden said, raising his voice to a shout. “What makes our moment rare is the freedom of democracy, under attack both at home and overseas.”

Mr. Biden’s speech had to accomplish several goals at once, including taking credit for an economy that has outperformed expectations but whose effects many Americans say they cannot feel. In a speech that ran for an over hour, he ran through a lengthy list of issues, including immigration, abortion, prescription drug costs and the war in Gaza.

He also engaged in a back-and-forth with congressional Republicans, picking up a button circulated by Republicans that called for people to say the name of Laken Riley, a Georgia nursing student who was killed in February.

The authorities have charged a Venezuelan migrant, who crossed into the United States illegally and was then released on parole, in the case.

Mr. Biden said Ms. Riley’s name, then added: “To her parents, I say, my heart goes out to you. Having lost children myself, I understand,” he said at one point, going off script and addressing Republicans by describing the accused as “an illegal.” The comment drew criticism from immigrant advocates and members of his own party who see the term as dehumanizing.

He also said there were thousands of murders committed by “legals.”

Mr. Biden used his time in front of one of the biggest audiences he will have before the November election to tell Americans that personal freedoms, diplomatic relationships and democratic rule in the United States are at stake if Mr. Trump is re-elected.

Mr. Biden assailed Mr. Trump for his soft treatment of President Vladimir V. Putin of Russia, whose troops invaded Ukraine more than two years ago. “If anybody in this room thinks Putin will stop in Ukraine, I assure you he will not,” Mr. Biden said, warning that the world was watching the United States.

“We will not bow down,” Mr. Biden said. “I will not bow down.”

He called out the former president’s behavior, including Mr. Trump’s lie that Mr. Biden had stolen the 2020 election from him.

“You can’t love your country only when you win,” Mr. Biden said.

Mr. Trump, never one to sit quietly, responded to many of Mr. Biden’s points in a stream of real-time posts on his social media site, Truth Social. “Putin only invaded Ukraine, because he has no respect for Biden,” he asserted in one post.

Ahead of the speech, Mr. Biden was under pressure to address the issue of his age. He laced his argument with humor — “I know I may not look like it, but I’ve been around a while,” he said, adding that his 81 years had taught him to “embrace freedom and democracy” and “to give hate no safe harbor.”

“Now some other people my age see a different story: an American story of resentment, revenge and retribution. That’s not me,” Mr. Biden said, a clear jab at his predecessor, who is four years younger and whose victory speech after Super Tuesday primary elections portended a dark future for America, a country he referred to as “third world.”

Mr. Biden also tried to quell dissatisfaction within his own party over his handling of the conflict in Gaza. Earlier on Thursday, the Biden administration said the United States would build a temporary seaport off Gaza to assist with the delivery of humanitarian aid.

“Israel also has a fundamental responsibility, though, to protect innocent civilians in Gaza,” Mr. Biden said.

The Israel-Hamas war has become a serious vulnerability for Mr. Biden. United Nations officials warn that famine is imminent in Gaza, and progressive voters of the Democratic Party are deeply angry with Mr. Biden’s support for Israel.

“To the leadership of Israel, I say this: Humanitarian assistance cannot be a secondary consideration or a bargaining chip,” he said. “Protecting and saving innocent lives has to be a priority.”

Of the hostages still held by Hamas, Mr. Biden said that his administration “will not rest until we bring every one of your loved ones home.”

Mr. Biden said, as he has before, that the Israeli-Palestinian conflict would not end without a two-state solution.

During his address, Mr. Biden focused extensively on reproductive rights, which have become a galvanizing issue for his party. Republicans cheered the Supreme Court’s decision in 2022 to overturn Roe v. Wade, which had established a constitutional right to abortion, but the party has been hurt in state elections since. Several women invited by the White House or Democratic lawmakers on Thursday evening had suffered life-threatening medical complications during pregnancy.

“Clearly those bragging about overturning Roe v. Wade have no clue about the power of women,” Mr. Biden said. “But they found out when reproductive freedom was on the ballot and we won in 2022, 2023, and we’ll win again in 2024.”

Mr. Biden, who once told supporters that he was “not big on abortion” because of his Catholic faith, promised to restore Roe’s protections — something that will be difficult to do without a sizable majority in Congress.

Mr. Biden had prepared for pushback from Republicans, who jeered him at different points during last year’s address, calling him a “liar” and breaking into mocking laughter. On Thursday, Mr. Biden ribbed Republicans at several points, including when he said that they had enjoyed taking credit for federal investments that they had voted against. At one point, a lawmaker yelled, “Lies,” as Mr. Biden spoke.

The speech was a high-stakes appearance for Mr. Biden, who is trailing behind Mr. Trump by five percentage points, according to a recent New York Times/Siena College poll.

Both men are unpopular, but Mr. Trump holds enormous influence over a far-right faction of House Republicans who defied members of their own party in rejecting a bill that would restrict immigration into the United States, saying it was not strict enough. Mr. Biden is under pressure to find a solution with a Republican Party that has so far signaled it will avoid giving him a political victory before November.

The share of Americans who view immigration as the biggest problem faced by the United States has risen in recent months, and a surge of undocumented immigrants has put the Biden administration on the defensive as the campaign gets underway.

And though inflation has come down and the job market has outperformed expectations, the data has done little to overcome a pervasive belief among many Americans that they simply are not better off than they were before. The Biden administration announced a plan on Thursday to lower housing costs for working families, and he explained how his economic policies had benefited families.

“It doesn’t make the news, but in thousands of cities and towns the American people are writing the greatest comeback story never told,” Mr. Biden said.

Within his economic message were hints about what Mr. Biden would do with a second term, including an effort to increase corporate taxes to at least 21 percent so, he said, “every big corporation finally begins to pay their fair share.” Such an initiative would be unlikely to succeed unless Democrats manage to hold the Senate and take back the House.

Republicans chose Senator Katie Britt of Alabama, who is nearly 40 years younger than the president, to deliver their response to Mr. Biden’s address.

“Our commander in chief is not in command,” Ms. Britt said. “The free world deserves better than a dithering and diminished leader.”

The 20 guests who joined Jill Biden, the first lady, to watch the address were all invited to draw sharp distinctions with Republicans on issues like reproductive rights, prescription drug prices and furthering Western diplomacy.

Mr. Johnson had his own guest list, highlighting people connected to issues that Republicans believe are vulnerabilities for Democrats, including crime, the opioid epidemic and immigration. He also invited Ella Milman and Mikhail Gershkovich, the parents of Evan Gershkovich, a reporter for The Wall Street Journal who has been imprisoned in Russia since last March.

Last weekend at Camp David, the president practiced for several days for his speech. On Thursday night, after days of media speculation on how he would seem during this speech, he took his time as he entered the chamber, stopping to take selfies with supporters.

At different points in his address, Mr. Biden appeared relaxed, to the point that he ad-libbed about Snickers bars and potato chip bags, and engaged in a back-and-forth with Republicans over tax breaks. After the speech, when the chamber was mostly cleared out, Mr. Biden was still there, shaking hands with some House members and holding forth on Ukraine.