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Good evening. Here’s the latest at the end of Monday.

1. President Biden made an unannounced trip to Ukraine, vowing “unwavering support.”

As air-raid sirens sounded, Biden strolled through the sunny streets of downtown Kyiv today with President Volodymyr Zelensky by his side. The American president had taken a 10-hour overnight train ride from the Polish border to arrive in the Ukrainian capital, which was buzzing with excitement.

Biden visited a famous monastery, announced $500 million in additional military aid for Ukraine and vowed to stand with the country “for as long as it takes.”

“One year later, Kyiv stands,” Biden said, four days short of the first anniversary of Russia’s invasion. “And Ukraine stands. Democracy stands.”

Biden’s visit, his first since the war began, was shrouded in secrecy. White House officials said they alerted Moscow several hours before the president arrived in Ukraine in an effort to “deconflict.”

The trip set up an increasingly direct confrontation with President Vladimir Putin of Russia. Tomorrow, both leaders will deliver speeches, 800 miles apart, vowing to stick with the war until the other retreats.

In related news, China accused the U.S. of spreading lies over claims that Beijing may be poised to send “lethal support” to help Russia’s war in Ukraine.

2. Another powerful earthquake struck Turkey and Syria, threatening more damage.

A 6.3-magnitude quake toppled buildings today in southern Turkey and northwestern Syria, stirring more panic in the region that was devastated this month by a 7.8-magnitude earthquake that killed more than 46,000 people and left more than a million homeless.

Many families still had bags packed from the first disaster.

The mayor of Hatay Province, where the epicenter of the tremor was, said that people were trapped underneath collapsed buildings. They had returned to their homes after the initial quake because they believed they were solid or to rescue their belongings, he added.

In related news, the U.S. secretary of state, Antony Blinken, pledged to help Turkey recover.

3. In Mississippi’s capital, a new court system has become a flash point.

Eighty percent of Jackson’s residents are African Americans, as are most of its elected leaders, judges and police officers. But a bill approved by the Republican-led state legislature would establish a separate court system, served by a state-run police force, for roughly one-fifth of the city — where the bulk of its white population resides. The proposed court system and police force would be controlled almost exclusively by white officials in the state government.

Republicans say the bill is a sincere effort to address the city’s soaring crime and court backlogs. But for many prominent Jacksonians, including the city’s Black Democratic mayor, the move evoked earlier eras in Mississippi’s complicated racial history.

“I was surprised that they came half-dressed, because they forgot to wear their hoods,” Mayor Chokwe Antar Lumumba said.

4. Chris Sununu is weighing a presidential bid on a message of de-MAGA-fied conservatism.

The New Hampshire governor has offered himself up as a referendum on the G.O.P. Sununu preaches fiscal conservatism and calls himself “pro-choice,” even though recent history finds little evidence that most Republicans are interested in a consensus-minded candidate.

But after three consecutive disappointing election cycles for his party, Sununu believes that he can appeal to Republican voters who have also grown impatient with Donald Trump.

“I’m not anti-Trump, I’m not pro-Trump,” Sununu said. “We’re just moving on.”

For more on the 2024 race: We asked Democratic voters about their views of a potential second term for Biden.

5. Prosecutors downgraded the manslaughter charges against Alec Baldwin.

Baldwin, who was holding the gun that discharged on the “Rust” movie set, killing the film’s cinematographer, faces significantly reduced possible prison time after the Santa Fe County district attorney’s office reduced the severity of the charges against him.

The change came after Baldwin’s lawyers argued that prosecutors had incorrectly charged the actor under a version of a New Mexico firearm law that was passed months after the fatal shooting in October 2021. Instead of a minimum five-year sentence, Baldwin now faces no more than 18 months in prison.

6. A hedge fund founder secured a retirement package worth billions.

Well over a decade after he first announced his planned retirement, Ray Dalio, the founder of the world’s biggest hedge fund, Bridgewater Associates, finally parted ways with the company late last year. His exit, partly spurred by remarks he had made dismissing concerns about China’s human rights record, followed more than six months of frantic negotiations.

Dalio, whose personal net worth is about $19 billion, agreed to surrender his control only if Bridgewater agreed to give him what could amount to billions of dollars in regular payouts through a special class of stock. It puts sharp pressure on the fund after returns have slipped.

7. Prison deaths spiked during the pandemic.

State and federal prisons experienced a nearly 50 percent increase in deaths in 2020 as the coronavirus swept across the country, according to the first comprehensive data on the issue. In six states they more than doubled.

The percentage rise in fatalities was more than twice that at the national level and even exceeded estimates at nursing homes. An aging inmate population, a correctional staffing shortage and ill-equipped medical personnel all combined to make prisoners especially vulnerable.

In other public health news, ketamine, the psychedelic-like drug, has become a popular treatment for mental health problems. Remote prescriptions of it are booming with little attention to the risks.

8. A 500-year-old da Vinci doodle revealed he was “far ahead” in understanding gravity.

Scientists discovered that Leonardo da Vinci did detailed experiments on gravity a century before Galileo and two centuries before Isaac Newton turned the study of the force into a science.

A manuscript in the British Library contained a da Vinci drawing demonstrating gravity as a constant force that resulted in a steady acceleration. Using an experiment with a crude setup but a brilliant design, da Vinci calculated the gravitational constant to within 10 percent of the modern value, a researcher said.

9. How one president’s birthday became Presidents’ Day.

Many Americans are off today in honor of the first president of the U.S., nearly 300 years after his birth. While George Washington was leading the Continental Army in 1778, a historian said, birthday celebrations were held, in part, “as a snub to King George.”

The contemporary idea of a Presidents’ Day — a nod to the birthdays of Abraham Lincoln and other presidents — came in 1968, when Congress designated certain holidays to be observed on Mondays. Officially, however, the holiday still only celebrates Washington.

For more: Alexis Coe, a Washington biographer, argues that the first president would hate Presidents’ Day.

10. And finally, a boardwalk game operator is found guilty of deception.

Anyone who has spent enough time on a New Jersey boardwalk is familiar with the time-honored tradition of small-time schemes: leaded milk bottles impossible to knock down and darts too dull to pop a balloon. One small agency is on a mission to eliminate the grift.

Last summer, investigators found that the operator of basketball games on the Wildwood boardwalk had consistently overinflated the balls, making them more likely to ricochet off the rim. Punishment included a $15,500 fine and a 10-year license suspension.

Have a trustworthy night.

Elizabeth Bristow compiled photos for this briefing.

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