North Vietnam’s capture of Saigon during the tumultuous days of April 1975 is a pivotal moment in Asia’s post-colonial history, but the story of what happened next is relatively little-known, both in and outside the country. Huy Duc, a veteran Vietnamese journalist, is aiming to shed new light on the reunification of Vietnam and its aftermath in a new book called “The Winning Side.”

Now based in Boston, Mass., where he is a Nieman fellow at Harvard University, Mr. Duc spent 20 years working in Vietnam, writing for local newspapers such as Tuoi Tre, Thanh Nien and Saigon Tiep Thi. He also published until 2010 the blogosin.org, which was ranked as the most popular blog in Vietnam, according to his Nieman profile.

For the past three years, he has worked on bringing reunification-era Vietnam to life through in-depth interviews with witnesses, including people who went on to become key post-war leaders in Vietnam and shapers of what is now one Asia’s most promising emerging economies....