When the signers of the Declaration of Independence pledged to each other “our Lives, our Fortunes and our sacred Honor,” they were describing precisely why we set aside Memorial Day to honor all who have died in service to our nation.

We often declare, rightly I think, that those who gave their lives for our country were fighting for freedom. But after a year marked by a searing confrontation with racial injustice, in the present and in our history, we would do well to ponder the military sacrifice of Black Americans from the Civil War forward. In World War II alone, 1.2 million Black Americans served in the military. What did freedom mean for those who faced racial oppression?

“Black men have fought in every single war for the United States, most of them at times when they weren’t even considered first-class citizens,” says Christopher S. Parker, author of “Fighting for Democracy: Black Veterans and the Struggle Against White Supremacy in the Postwar South.”

In his interviews with Black veterans, Parker, a political science professor at the University of Washington, found a patriotism rooted not in the reality of their moment but in aspirations for the future — “hope that America would recognize its founding values. It’s the thing that kept them going,” he told me.

Black Americans’ military service has been key to later advances in equal rights from the time of the Civil War, when formerly enslaved people signed up to fight for the Union. Their units, Parker notes, were separately designated as “United States Colored Troops.”

“President Lincoln, a late convert to allowing Black men to fight in the war, himself declared that without the role of the Black soldiers, the war would not have been won,” says Henry Louis Gates, university professor and director of the Hutchins Center for African and African-American Research at Harvard University.

Black military service had a direct relationship to “the achievement of the rights of citizenship,” Gates told me. “In Lincoln’s final speech, he tentatively floated the idea of Black male suffrage for the men who had played such a decisive role in the Union’s victory and for a small group of ‘very intelligent’ Black men. Some scholars argue that this statement led to Lincoln’s assassination, since John Wilkes Booth was in the audience and essentially said that this was the last straw.”

Gates, whose books include “Stony the Road: Reconstruction, White Supremacy and the Rise of Jim Crow,” noted that “Lincoln’s mostly southern ‘black warriors’ (as he called the Black soldiers in 1864) would, along with northern Black abolitionists, ministers, and free Black men in the South, go on to play key roles in Reconstruction.”

If the Civil War was unquestionably a battle for freedom, so was World War II. It led, as Gates noted, to the “Double V” campaign in the Black community, “victory over fascism abroad, and simultaneously victory over anti-black racism at home.”

In his magisterial book “From Slavery to Freedom,” the late historian John Hope Franklin showed how racial subjugation stood in direct contradiction to the war aims President Franklin D. Roosevelt outlined in his Four Freedoms speech.

“The experience of living in two worlds had prepared Negroes to wage two fights simultaneously,” Franklin wrote. “They felt compelled to carry on the fight for better treatment at home so as to give real meaning to the ideal of the Four Freedoms.”

Franklin cited the words of Eleanor Roosevelt, who advocated for civil rights far more forcefully than her husband. “The nation cannot expect colored people to feel that the United States is worth defending,” she said early in the war, “if the Negro continues to be treated as he is now.”

Service in World War II and later in Korea were crucibles for future civil rights leaders. Parker noted that Hosea Williams served in an all-Black unit under Gen. George Patton. In 1965, with a young John Lewis, Williams would lead voting-rights marchers across the Edmund Pettus Bridge in Selma, Ala. Jackie Robinson, who would integrate Major League Baseball, was an Army lieutenant. In 1944, he refused to move to the back of an Army bus. He was court-martialed but acquitted.

“A lot of people talk about patriotism these days,” Parker told me. “But what is patriotism? It’s a commitment to a set of founding values so complete that one is willing to make the ultimate sacrifice.”

This can be said of all we honor on Memorial Day. But Parker and Gates, like Franklin before them, are right to call our attention to Black Americans who served and sacrificed on the basis of what the Rev. Martin Luther King Jr. called “a promissory note,” written in our founding documents — one that still awaits full payment. It’s hard to imagine a more sweeping sense of faith — and hope.

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