On April 30, 1975, Vu Dang Toan commanded the first tank to smash through the main gate of Saigon’s Independence Palace. After seeing so many die — after grinding away his youth battling the Americans and the forces of South Vietnam — he was there, alive and surprised, for the war’s weary end. It was a full surrender. At the United States Embassy nearby, helicopters had already carried away the last Americans as the South’s fighters disappeared, ditching their uniforms and boots in the streets. “I’m proud,” Mr. Toan said, “that as a soldier, I completed the mission.” Fifty years later, he was a long way from that moment, sitting in his comfortable home north of Hanoi, encircled by rice fields, not far from factories pumping out Apple Watches. Photos on the wall showed his tank on the palace lawn. Wearing his military uniform, he sipped tea in a dark wood chair beside his grandson Dang Hoang Anh, 14, a bright-eyed soccer fan wearing a school uniform in Chelsea blue. The boy pictured his life in different terms. His goal? “To study in Canada.” His mission? “To make money.” “My grandparents’ generation, they had to go to war and people died,” Hoang Anh said. “Now we don’t worry about that. We worry about school and jobs.”