You’ve heard of the Vietnam War, but what about the “secret war” in Laos? Over 16 million members of the Greatest Generation fought in World War II, but what about the 5.8 million Americans who served in the “Forgotten War?” History is full of conflicts that have become footnotes in American history books—if they make it in at all. Here are five secret or forgotten wars that are commonly overlooked.

1. Philippine-American War

The Philippine-American War
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American troops fire on insurgents in the Philippine jungle during the Philippine-American War, circa 1899.

During the Spanish-American War, rebels in the Philippines proclaimed their independence after 300 years of Spanish rule… only to have their hopes for a free nation written off with a few pen strokes when the Treaty of Paris was signed in 1898, handing the Philippines to the United States. Rebel leader Emilio Aguinaldo—who had convened a revolutionary assembly that drew up the first democratic constitution in Asia—launched a revolt. 

The United States responded by sending in troops and by war’s end, over 4,000 American soldiers had died, ten times the number of Americans killed in the Spanish-American War. Losses among locals were worse: 20,000 Filipino insurgents and an unknown number of civilians lost their lives in the fight for independence.

David Silbey, associate director, Cornell in Washington and author of A War of Frontier and Empire: The Philippine-American War, 1899-1902, writes that the Philippine-American War “was our last war of manifest destiny and western expansion and our first imperial land war in Asia. It was the United States testing out what role it would have on the world stage and bringing with it all the complicated racial and cultural attitudes that shaped American society at home.”

2. The Korean War: ‘The Forgotten War’

The Korean War (1950-1953) was the first military action of the Cold War, though it’s often overshadowed by the victory of the Allies in World War II, earning it the nickname “the Forgotten War.” It began when soldiers from the communist North Korean People’s Army crossed the 38 parallel into the pro-Western Republic of Korea (today’s South Korea). American troops were sent to support the South and by the time a ceasefire was proclaimed in 1953, over five million soldiers and civilians had died. To this day, a formal peace treaty has not been signed.

Sheila Miyoshi Jager, professor of East Asian Studies at Oberlin and author of Brothers at War: The Unending Conflict in Korea, writes, “Most histories of the Korean War stop with the armistice; the fact that no peace treaty was ever signed is presented in most history books as an unusual fact and that is all. However, the absence of a final conclusion to the Korean War has kept it alive as a major influence on Asian affairs.”

3. The ‘Secret War’ in Laos

Bombings in Laos
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Bomb craters dating to the Vietnam War are seen in Xiang Khwang province of Laos, photographed in 1991.

Laos is the most heavily-bombed country per capita in the world. The U.S. bombing of Laos (1964-1973) was part of a clandestine attempt by the CIA to wrest power from the Pathet Lao, a communist group allied with North Vietnam and the Soviet Union during the Vietnam War. Laos was critical to Dwight D. Eisenhower’s Domino Theory of keeping communism at bay, and presidents John F. Kennedy, Lyndon B. Johnson and Richard Nixon all escalated the bombings, which largely targeted North Vietnamese supply routes along the Ho Chi Minh Trail that stretched from Vietnam into Cambodia and Laos.

While the U.S. invasion and bombing of Cambodia drew international protests, The Secret War in Laos remains largely shrouded in secrecy even as it marked the beginning of a more militarized CIA that would go on to fight proxy wars in Latin America and the Middle East.

4. Cambodian Genocide

U.S. bombing of Cambodia
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The aftermath of heavy bombing in Snuol, Cambodia, during the Cambodian Campaign of the Vietnam War, photographed May 11, 1970.

The Cambodian genocide (1975-1979) led to the deaths of over two million people at the hands of Pol Pot and the Khmer Rouge—and was exacerbated by the U.S. bombing and invasion of Cambodia. Vaddey Ratner, author of In the Shadow of the Banyan and Music of the Ghosts, and a survivor of the genocide, writes, “While the Khmer Rouge genocide is a tragedy perpetrated by Cambodians, the U.S. aerial bombing campaign created the destruction and chaos that enabled the Khmer Rouge to seize power. That bombing, extending for eight years and long kept secret from the American public, was, in the eyes of American officials, a ‘sideshow’ to the war in Vietnam.”

5. American-Indian Wars

The Battle of Little Bighorn.
The Battle of Little Bighorn/credit: Buyenlarge/Getty Images
The Battle of the Little Bighorn, also known as 'Custer's Last Stand.'

Many elementary school students in the United States are introduced to Native Americans in the context of the First Thanksgiving. They don’t reemerge until they become side notes in lesson plans on Manifest Destiny and the American West—a narrative that often ends at Wounded Knee in 1890. The term “The American-Indian Wars” groups multiple conflicts between diverse tribes and settlers spanning nearly three centuries of American History.

David Treuer, author of The Heartbeat of Wounded Knee, writes, “Rather than a sidebar to American history proper, Native American history IS American history. You can't, for example, understand the American Revolution without considering that one of the main reasons for revolt against Britain was over the question of whether the colonists or their British masters got to reap the benefit of westward expansion; you can't understand the tension between states' rights and federal power unless you understand the removal of the 5 Civilized Tribes from the American Southeast in the 1820s and ‘30s and how that paved the way for the expansion of slavery…Native people have been, since the beginning, involved and implicated in the making of America.”

HISTORY Vault: Korea: The Forgotten War

Five years after WWII, America is once again plunged into bloody battle. Robert Stack hosts this penetrating documentary about the war in Korea.