Andrew Zimmerman is professor of history at the George Washington University. He is writing an international history of the American Civil War.

The Stars and Stripes held the place of honor at the 1865 festivities of the International Workingmen’s Association, Karl Marx’s London-based organization of socialists, communists, anarchists and trade unionists. To Americans raised in the ideological climate of the Cold War, the U.S. flag and Karl Marx might seem an odd juxtaposition, but to 19th-century working-class radicals, the triumph of the United States over the slaveholding Confederacy represented a victory not only for the formerly enslaved but also for workers everywhere.

For revolutionary socialists, the Civil War was a decisive victory in an even larger struggle between democracy and private property.

Slavery, for Marx and other radicals, was an especially cruel version of a much broader conflict between democracy and the rights of property owners. The Confederate bombardment of Fort Sumter began what Marx, in an 1864 letter to President Abraham Lincoln, called a “general holy Crusade of Property against Labour.” By claiming to own people, a wealthy elite in the South accorded to itself the right not only to brutalize their "property" but also to take for themselves the wealth created by four million African-American workers. Elsewhere, wealthy elites claimed similarly that their ownership of factories gave them the right to manage, and to live off the work of, "their" employees.

Marx had been calling for the “emancipation” of workers through the “abolition” of oligarchic concentrations of property -- capital -- for decades. The emancipation of the enslaved through the abolition of slavery represented a world-transforming step in this direction.

Marx also followed the progress of the Civil War closely because so many of his fellow exiled European revolutionaries fought in the ranks of the Union Army. Defeated and sent into American exile after a wave of European revolutions in 1848-49, many discovered in the struggle against slavery more hopeful strategies than any they had previously pursued.

Revolutionary socialists were thus one of the many groups that won the Civil War. For them, it was a decisive victory in an even larger struggle between democracy and private property. More conservative elites, northern as well as southern, sought to limit the scope of emancipation even before the Confederate surrender at Appomattox. They continue to do so, as we saw last week with the Supreme Court’s decision on the Voting Rights Act of 1965. Yet the example of this successful democratic revolution against oligarchic property remains as powerful today as it was a century and a half ago when Karl Marx cheered for the Red, White and Blue.