Russia has started the largest war in Europe since World War II.

China has become more bellicose toward Taiwan.

India has embraced a virulent nationalism.

Israel has formed the most extreme government in its history.

And on Saturday morning, Hamas brazenly attacked Israel, launching thousands of missiles and publicly kidnapping and killing civilians.

All these developments are signs that the world may have fallen into a new period of disarray. Countries — and political groups like Hamas — are willing to take big risks, rather than fearing that the consequences would be too dire.

The simplest explanation is that the world is in the midst of a transition to a new order that experts describe with the word multipolar. The United States is no longer the dominant power it once was, and no replacement has emerged. As a result, political leaders in many places feel emboldened to assert their own interests, believing the benefits of aggressive action may outweigh the costs. These leaders believe that they have more sway over their own region than the U.S. does.

“A fully multipolar world has emerged, and people are belatedly realizing that multipolarity involves quite a bit of chaos,” Noah Smith wrote in his Substack newsletter on Saturday.

Zheng Yongnian, a Chinese political scientist with ties to the country’s leaders, has similarly described the “old order” as disintegrating. “Countries are brimming with ambition, like tigers eyeing their prey, keen to find every opportunity among the ruins of the old order,” Zheng wrote last year.

Why has American power receded? Some of the change is unavoidable. Dominant countries don’t remain dominant forever. But the U.S. has also made strategic mistakes that are accelerating the arrival of a multipolar world.

Among those mistakes: Presidents of both parties naïvely believed that a richer China would inevitably be a friendlier China — and failed to recognize that the U.S. was building up its own rival through lenient trade policies, as the political scientist John Mearsheimer has argued. In Afghanistan and Iraq, the U.S. spent much of the early 21st century fighting costly wars. The Iraq war was especially damaging because it was an unprovoked war that George W. Bush chose to start. And the humiliating retreat from Afghanistan, overseen by President Biden, made the U.S. look weaker still.

Perhaps the biggest damage to American prestige has come from Donald Trump, who has rejected the very idea that the U.S. should lead the world. Trump withdrew from international agreements and disdained successful alliances like NATO. He has signaled that, if he reclaims the presidency in 2025, he may abandon Ukraine.

In the case of Israel, Trump encouraged Benjamin Netanyahu, Israel’s prime minister, to show little concern for Palestinian interests and instead seek a maximal Israeli victory. Netanyahu, of course, did not start this new war. Hamas did, potentially with support from Iran, the group’s longtime backer, and Hamas committed shocking human rights violations this past weekend, captured on video.

But Netanyahu’s extremism has contributed to the turmoil between Israel and Palestinian groups like Hamas. An editorial in Haaretz, an Israeli newspaper, yesterday argued, “The prime minister, who has prided himself on his vast political experience and irreplaceable wisdom in security matters, completely failed to identify the dangers he was consciously leading Israel into when establishing a government of annexation and dispossession.” Netanyahu, Haaretz added, adopted “a foreign policy that openly ignored the existence and rights of Palestinians.”

Even with the rise of multipolarity, the U.S. remains the world’s most powerful country, with a unique ability to forge alliances and peace. In the Middle East, the Trump administration persuaded Israel and four other countries — the United Arab Emirates, Bahrain, Sudan and Morocco — to sign unprecedented diplomatic agreements, known as the Abraham Accords. In recent months, the Biden administration has made progress toward an even more ambitious deal, between Israel and Saudi Arabia.

Hamas attacked Israel in part to undermine an Israeli-Saudi deal, many experts believe. Such a deal could isolate Iran, Hamas’s patron, and could lead to an infusion of Saudi money for the Palestinian Authority, a more moderate group than Hamas (as Thomas Friedman explains in this column). But if the recent Hamas attacks lead Israel to reduce the Gaza Strip to rubble in response, Saudi Arabia will have a hard time agreeing to any treaty.

“This will slow considerably if not kill the Saudi Abraham Accords deal,” Mara Rudman, a former U.S. diplomat, told The Times.

In these ways, you can think of Hamas’s attacks as an attempt to prevent a reassertion of American power — and instead to continue pushing the world toward multipolarity.

I understand that some readers may question whether the long era of American power that’s now fading was worth celebrating. Without question, it included some terrible injustices, be they in Vietnam, Iran, Guatemala or elsewhere. But it also made possible the most peaceful era in recorded history, with a sharp decline in deaths from violence, as Steven Pinker noted in his 2011 book, “The Better Angels of Our Nature.” And the number of people living in a democracy surged.

Smith concluded his Substack newsletter on the new Middle Eastern war this way:

Over the past two decades it had become fashionable to lambast American hegemony, to speak derisively of “American exceptionalism,” to ridicule America’s self-arrogated function of “world police” and to yearn for a multipolar world. Well, congratulations, now we have that world. See if you like it better.

  • Israel is fighting to retake towns and ordered a “complete closure” of Gaza. More than 700 people have died in Israel.

  • Israel just struck a marketplace in Gaza, and hundreds of other strikes have leveled whole buildings and homes. At least 493 Palestinians have died.

  • “Everyone was surprised”: Palestinians also said they were shocked by the Hamas attack. This video shows the destruction in Gaza.

  • Thousands of Israeli soldiers and tanks are on the southern border with Gaza, a possible prelude to a ground assault. “We are embarking on a long and difficult war,” Netanyahu said.

  • Hamas and other militants are holding an estimated 150 hostages. They could become human shields or bargaining chips.

  • Militants killed ravers and took hostages at a music festival just after dawn on Saturday. Read how the massacre unfolded and watch a video of one abduction.

  • The Pentagon announced it would send munitions to Israel and move Navy warships, including an aircraft carrier, closer to the region.

  • People demonstrated in solidarity with the Palestinians across the Middle East.

  • The failure of Israel’s intelligence agencies to foresee the attack could affect their reputation — and the political future of Netanyahu.

  • In his bid for House speaker, Representative Steve Scalise is pitching himself as a candidate that can unite Republicans.

  • Puerto Rico is adding “USA” to the top of its driver’s licenses, after high-profile cases of people being told their identification isn’t proof of American citizenship.

  • Many U.S. cities and states are observing Indigenous Peoples’ Day today. Read about the history behind it.

  • The Powerball Jackpot has grown to $1.55 billion.

Music diplomacy programs can help normalize U.S.-China relations, just as Ping-Pong did in the 1970s, Carla Dirlikov Canales, an opera singer, writes.

Meet Lewis: A talking $180 Target jack-o’-lantern has become a must-have Halloween decoration. He insists you call him by his name.

Connections: For some teenagers, LinkedIn is a sanctuary from the angry rants and thirst traps of other social-media networks, The Cut reports.

Metropolitan Diary: Perching on Playbills instead of cushions.

Lives Lived: Claude Cormier was an avant-garde Canadian landscape architect known for playfully subversive designs that confused officials and delighted residents. He died at 63.

Sunday night football: The 49ers remain undefeated after clobbering the Cowboys, 42-10, in an impressive performance.

Around the N.F.L.: The Detroit Lions steamrollered the Carolina Panthers, 42-24, in a game that wasn’t close after the second quarter. The Miami Dolphins made history in their 31-16 win against the New York Giants: Their 2,599 yards were the most by any team five games into the season in the Super Bowl era.

An oral history: Ten years ago this month, “12 Years a Slave,” directed by Steve McQueen and written by John Ridley, was released. It was a serious R-rated Black drama with no movie stars — but it went on to gross nearly $190 million. “The movie arrived in Hollywood like a U.F.O. landing,” writes the Times reporter Reggie Ugwu, paving the way for the landmark films “Selma” (2014) and “Moonlight” (2016).

Read an oral history of the making of the film from McQueen, Hans Zimmer, the film’s producers and others.