“Nobody can soldier without coffee,” a Union calvary man wrote in 1865. Hidden Kitchens looks at three American wars through the lens of coffee: the Civil War, Vietnam and Afghanistan. And an interview with Anastacia Marx de Salcedo author of “Combat Ready Kitchen: How the U.S. Military Shapes the Way You Eat.”

The Civil War: War, freedom, slavery, secession, union – these are some of the big themes you might expect to find in the diaries of Civil War soldiers. At least, that’s what Jon Grinspan, a curator at the Smithsonian’s National Museum of American History, assumed when he began digging through war journals in the nation’s Civil War archives. “I went looking for the big stories,” Grinspan says. “And all they kept talking about was the coffee they had for breakfast, or the coffee they wanted to have for breakfast.”

The Vietnam War: Coffee may have powered the Union army during the Civil War, but during the Vietnam War, it fueled the GI anti-war movement. In the late 1960s and early ‘70s, as soldiers returning from Vietnam began to question the U.S. role in the war, GI coffeehouses sprung up in military towns outside bases across the country. They became a vital gathering place. Oleo Strut, Fort Hood, TX, Shelter Half, Tacoma, Washington, the Green Machine outside Camp Pendleton, San Diego; Mad Anthony Wayne’s, Waynesville, Mo., outside Fort Leonard, to name a few. As the anti-war movement heated up, these coffeehouses became places where GIs could get legal counseling on issues like going AWOL and obtaining conscientious objector status, and learn about ways to protest the war.

Afghanistan: “ The military runs on coffee,” says Harrison Suarez, co-founder of Compass Coffee in Washington DC. “The Marines especially. It’s this ritual.” Suarez and Michael Haft, who started Compass together, first became friends in the Marines over coffee learning how to navigate with a map and compass.

As the war in Afghanistan intensified, both Suarez and Haft deployed there with the 1st Battalion, 9th Marines. One of their missions was to help develop the local police force and army. The two men tried to bond with their new Afghan partners over coffee, but the Afghans weren’t having it. The Afghan culture is much more about tea. Regardless of what was in the cups, the experience of gathering together over a hot drink and “taking time to develop a rapport with your partners that you are fighting alongside holds the same.”

This story is part of the Hidden Kitchens series “Kimchi Diplomacy: War and Peace and Food.”