America's Secret War in Laos Uncovered

— -- This week, Barack Obama became the first sitting U.S. president to visit the Southeast Asian nation of Laos. In making it his last stop on his last official trip to Asia, Obama wanted to turn the page on this painful chapter of U.S. history.

Inside Laos: The Secret American War

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During the height of the Vietnam War, the United States dropped more bombs on neighboring Laos than over Germany and Japan in World War II combined. Thirty percent of those bombs did not explode. ABC News' Bob Woodruff returns to Laos to speak with victims and their families to see how America's "secret war" has impacted their lives. One of the temples in Vientiane, Laos.

Kaijing Xiao/ABC News

During the height of the Vietnam War, the U.S. conducted another war in secret in Laos, on Vietnam's western border, in an attempt to destroy communist supply lines. More bombs were dropped on Laos than over Germany and Japan in World War II combined. From 1964 to 1973, Laos was one of the most heavily bombed countries per capita in history.

However, 30 percent of the bombs dropped did not explode, and to this day, armed and active devices litter the country. Since the bombings stopped, tens of thousands of Lao have been killed or maimed by this unexploded ordnance, and 40 percent of the victims are children.

More than 40 years after the war, one-third of the country is still contaminated by unexploded ordnance — an ongoing cost of war that affects the Lao people daily.

As Obama makes his historic visit, ABC correspondent Bob Woodruff travels across Laos, meeting victims new and old bearing witness to the legacy left behind by America’s secret war.