A year ago, rebels overthrew President Bashar al-Assad, ending decades of dictatorship and civil war. But challenges remain for the new leadership.

Fireworks lit the sky and music blared on Monday in the center of Syria’s capital, Damascus, as tens of thousands of people celebrated the first anniversary of the fall of the dictator Bashar al-Assad and the end of his family’s decades-long tyrannical rule.

The festivities come as the country grapples with sectarian violence, deep economic challenges and security gaps that hinder any meaningful recovery. Its new leaders are also contending with how to build institutions that govern equitably for Syria’s estimated 25 million people, while balancing competing regional interests and navigating longstanding social, political and religious divisions.

But a year after Mr. al-Assad was overthrown, many Syrians united in joy in their newfound freedom.

Beginning at dawn, thousands of people thronged the historic Umayyad Mosque in Damascus as the call to prayer rang out through the cold, still air. Among them was President Ahmed al-Sharaa, who arrived before sunrise. Billboards, with slogans like “One country, one people” and “The dark era is over,” lined the streets, reminding people of what they had endured — and what they were now celebrating. Hours later, a military parade featuring horses, motorcycles, tanks and helicopters took center stage.

People are silhouetted against a wall of black and white photographs of people who died during the Syrian civil war. — Syrians walking past photographs of people who died during the war, which were put on display by the new defense ministry.

A woman takes a photograph of a friend who is standing behind a poster of a soldier in fatigues holding a gun. — A child is photographed posing behind a cutout poster of a soldier at a military expo set up by the new defense ministry.

“The oppression has ended,” said Mohamed Hariri, 48, a trader in Damascus who is originally from Dara’a, in southwestern Syria. “We now remain optimistic about the future.”

Mr. Hariri’s optimism was a stark contrast to the fear people felt under the Assad dynasty, which ruled Syria for more than five decades. Under both Bashar al-Assad and his father, Hafez al-Assad, the regime maintained control with an iron fist, silencing dissent through torture, imprisonment and fear.

But all of that came undone last December, as rebels seized government strongholds, broke through army posts and swiftly captured the capital. Mr. al-Sharaa, a former commander of a rebel group allied with Al Qaeda, emerged as Syria’s de facto leader and quickly set out to restore the country’s international standing.

A horse rears during a military parade. — A horse rears up during the military parade in Damascus on Monday.

Crowds gather in a roundabout to watch a military parade. — Crowds gathered to watch a military parade in central Damascus on Monday.

Mr. al-Sharaa met with President Trump and spoke at the United Nations in September, the first time a Syrian leader had done so in almost 60 years. He succeeded in getting the United States to lift most of the sanctions that had crippled its economy. He urged international investors to fund Syria’s reconstruction through investment and trade.

“The end of our battle with the defunct regime only meant the start of a new battle in the fields of work, diligence and dedication,” Mr. al-Sharaa said in a speech on Monday evening, donning the same outfit he wore when his forces rolled into Damascus a year ago. “It is a battle of aligning words with action, promises with delivery and values with practice.”

Yet despite the optimism from the president and many Syrians, worries persist.

A group of men dance and hold flags under a string of lights. — Syrians dancing amid the ruined buildings of Jobar, a neighborhood in Damascus that was destroyed during the war.

Officers in riot gear push back against a crowd of men, many of whom are holding up phone cameras. An ornate building and red carpeting can be seen in the background. — Syrian riot police officers pushing back a crowd of men trying to see President Ahmed al-Sharaa at Umayyad Mosque in Damascus on Monday.

Cuts to bread and fuel subsidies have left citizens struggling with rising prices. Some Syrians who spoke to The New York Times in recent days expressed frustration over the government prioritizing billboards advertising the anniversary and luxury cars for officials. With few job opportunities and low wages, some young Syrians see emigration as their only hope for a better future.

“I see no development nor any hope,” said Azab Toumeh, 30, who works in a vegetable and fruit market in Damascus. She earns $6 a day, she said, and cares for her sister and 14 children, including her brother’s children, who were orphaned after he was killed in the war.

Syria’s challenges have been made worse by the immense task facing Mr. al-Sharaa’s government in navigating a fractured society. Sectarian violence has killed thousands over the past year. In March, armed men killed more than 1,600 civilians, mostly from the Alawite minority, to which Mr. al-Assad belongs. In July, clashes between Druse fighters, another minority group, and government forces in the southern province of Sweida killed hundreds.

A defaced poster of a Bashar al-Assad, the former leader of Syria. — A defaced poster of Bashar al-Assad, the former leader of Syria, who was ousted a year ago.

A man on horse and two other men holding guns next to a ruined building. — Syrian men gathering next to ruined buildings in the destroyed area of Jobar.

“We were dreaming of building a country together,” said Najwa Altaweel, a 53-year-old human rights activist from Sweida. But after the killings there, that optimism disappeared. “We were left with disappointment, and our dreams vanished.”

Fidaa Deeb, a gynecologist in the coastal province of Latakia, said many Alawites, except for those in Mr. al-Assad’s inner circle, were marginalized and had hoped for change after his ousting. However, Mr. Deeb noted that discrimination has persisted, with job dismissals and withheld salaries fueling discontent.

“Our feeling today is one of fear and apprehension,” he said by phone. “The same mistakes of the previous regime are being repeated.”

On Saturday, the Kurdish-led administration in the northeast banned any public gathering commemorating the anniversary, citing security concerns. The administration has rejected Mr. al-Sharaa’s push for central control and the relationship between the two sides remains fraught.

An armed member of the Syrian security forces stands on a rooftop as thousands of people gather in a central square below. — A member of the Syrian security forces standing on a rooftop as thousands of people gathered in the central square of Hama, Syria, on Friday.

Syrian women and girls hold portraits of deceased or missing loved ones. — Syrian women and girls holding portraits of deceased or missing loved ones in the Damascus neighborhood of Jobar on Sunday.

“The rotten regime of Bashar is gone, but we are all in fear of what could happen next,” said Zinan Othman, 47, who runs an appliance store in Wadi al-Mashari, a Kurdish-populated neighborhood in Damascus. “Nobody is being punished for incitement.”

For many, the celebration was bittersweet, especially those with loved ones who are still missing. Tens of thousands of people deemed opponents of the Assad regime had been arrested by the former authorities and disappeared, and many were executed, according to human rights groups.

Sharifa Hazber, 51, last saw her husband, Basil, in 2018 at Sednaya, Syria’s most notorious prison. At an event for families of the missing and martyrs, she said she wanted the government to reveal what had happened to him, provide any clues or share any documents related to his case so that she can find closure.

“I need to know if he was shot, if he was hanged or anything that happened to him,” she said. “It is my right.”