HO CHI MINH CITY, Vietnam — This city once known as Saigon was blanketed Thursday in red banners that read “Long Live the Glorious Communist Party of Vietnam,” 40 years after northern forces seized control of the country and America walked away from a divisive and bloody war that remains a painful sore.

Thousands of Vietnamese, including war veterans in uniforms heavy with medals, lined up to watch goose-stepping soldiers and traditional performers parade through the streets of what is now Ho Chi Minh City.

On April 30, 1975, North Vietnamese tanks rolled into Saigon, then the capital of South Vietnam. They crashed through the gates of the presidential palace and hoisted the communist flag. It was an incredible victory for the revolutionary forces that had waged guerrilla warfare for more than a decade against the better equipped United States, and before that against the French colonialists.

“The tank crashing the gates … was a symbol of victory for the Vietnamese nation and the Vietnamese People’s Army, marking the end of the 30 years of national resistance against the French and then the Americans,” said Nguyen Van Tap, 64, who drove Tank 390 through the iron bars and reunited with members of his company Wednesday.

And even after four decades, he said, the winners who fought for the north should be given priority and privileges over those who were branded traitors for siding with South Vietnam.

“For the Vietnamese,” he said, “April 30 is a day of festivities and national reunification.”

For the United States and its South Vietnamese allies, the day was one of panic, chaos and defeat known simply as the fall of Saigon.

After the government’s parade and celebratory speeches were over Thursday, a group of former U.S. Marines who helped Americans evacuate Saigon as it fell gathered at the site of the old U.S. Embassy, now the U.S. Consulate, for a somber ceremony. They dedicated a plaque to two fallen comrades who were the last U.S. servicemen killed in the war. Cpl. Charles McMahon and Lance Cpl. Darwin Judge died April 29, 1975, when their post near the airport was hit by a rocket. Each of the former Marines placed roses in front of the monument before saluting it as taps played.

Some 58,000 Americans were killed in the war, along with up to 250,000 South Vietnamese allies and an estimated 3 million communist fighters and civilians.

Hundreds of thousands of Vietnamese fled South Vietnam in the days and years after the war, with many taking rickety boats in search of freedom. The majority ended up resettling in the United States. Many have since returned to visit family.