Inspired by the story of a distant cousin, investigative journalist Julia Harte explores the rich and hidden history of American citizens who fought against imperialism and dictatorship abroad, only to be excoriated at home.

One night in 1940, a group of Stalinists opened fire on Leon Trotsky’s compound in Mexico City. In the end, the victim was not Trotsky, but his bodyguard: a young American named Sheldon Harte. For investigative journalist Julia Harte, the quest to uncover the truth about Sheldon–her father’s second cousin–was just the beginning of discovering a wider, hidden history of Americans who traveled abroad to join revolutionary liberation movements–and in return were labeled radicals by the U.S. government.

From Americans who fought in the 19th-century Greek revolution to modern-day solidarity volunteers in Palestine, Harte chronicles two centuries of Americans whose support for international causes at odds with U.S. geopolitical interests put them in their own government’s crosshairs. The surprising characters she profiles include African American volunteers in the Spanish Civil War who battled bigotry and McCarthyism upon returning home; a Jewish American woman who helped the Black Panthers establish an international wing in post-independence Algeria; a teenage activist who organized Filipinos against the repressive Marcos regime; the forgotten Native American contingent in Nicaragua’s Sandinista-Contra conflict; and many more. These figures held various ideologies and beliefs, yet each in their own way sought to fight oppression and saw their actions as grounded in American ideals of equality, self-government, and human rights. Meanwhile, U.S. officials responded to them with surveillance, blacklists, travel bans, and prosecution.

Through meticulous research and on-the-ground reporting, Harte brings her subjects to life in deeply personal detail, exploring not only their heroic sides but also the tensions between their actions and ideals. Interrogating how and why activists were branded as threats by an expanding security state, Harte asks what makes a ‘radical’. In lively narrative and rich detail, this eye-opening book reveals the long history of transnational radicalism as an irrepressibly American tradition.