If tea was the drink that unofficially launched the American Revolution, then coffee—or “cups of Joe”—fueled the G.I. Joes of World War II. Every American soldier’s C-rations contained coffee.

“Soldiers overseas craved a sense of normalcy,” says Sarah Wassberg Johnson, The Food Historian. “Having a hot, comforting beverage that brought pleasure was a big deal.”

Coffee increased energy and alertness on the battlefield, improved morale and was even used by medics to help prevent shock.

“The use of stimulants has a long history on the battlefield, and caffeine is one of the milder options,” says Johnson. (Stronger options have included alcohol and amphetamines.) “If you’re up all night in battle, coffee can help you get back on your feet.”

American troops have run on coffee since The American Revolution. After the British imposed a tax on tea, drinking coffee was seen as the patriotic alternative. (Though not without an adjustment period—in a letter to his wife Abigail, future president John Adams lamented: “I have drank Coffee every Afternoon since, and have borne it very well. Tea must be universally renounced. I must be weaned, and the sooner, the better.”)

During the Civil War, Union soldiers were issued 36 pounds of coffee annually. Northern troops went to great lengths to brew their daily cup: “Yankees brought raw beans with them, roasted them in frying pans, then ground them up. They even built grinders into guns,” says Mark Pendergrast, author of Uncommon Grounds: The History of Coffee and How It Transformed Our World. Meanwhile, Confederate troops, deprived of coffee, made do with roasting substitutes like acorns and barley. “Anyone who is a caffeine  addict knows what happens when you don’t get caffeine,” Johnson says.

In World War I, the U.S. War Department took a direct role in coffee production, establishing roasting and grinding plants in France so soldiers would have access to coffee in the trenches. Returning troops brought their taste for coffee home and by the mid-20th century, coffee was an essential part of Americans’ morning routine. From 1900 to 1946, U.S. annual per-capita coffee consumption doubled, reaching 19.8 pounds by 1946.

Did you know? During World War II, First Lady Eleanor Roosevelt hosted a radio show called “Over Our Coffee Cups” with the tagline “Get More Out of Life with Coffee.”

During World War II, nearly 10 percent of all U.S. imports were coffee beans. “The military supplied defense workers and troops with as much coffee as they could drink,” says Pendergrast. Increased military demand for coffee was compounded by a threatened supply chain. As the war intensified, civilian vessels were commandeered by the U.S. Merchant Marines, meaning fewer ships were available for transporting beans. Those that did attempt the journey were threatened by German U-Boats patrolling trade routes.

After the Japanese attack on Pearl Harbor on December 7, 1941, coffee prices were fixed to control inflation. The U.S. Navy bought most of Hawaii’s Kona coffee crop and established their own roasting plants in strategic locations like Oakland, Brooklyn, and on Hawaii itself. As Samuel Eliot Morison wrote in his 1947 volume on the history of the U.S. Navy, “although the United States Navy might win a war without coffee, it hopes never to be forced to make the experiment.”

In June of 1942, Brazil—one of the largest suppliers of coffee beans to the U.S.—turned over its ships to the Allies in exchange for a promise that the U.S. Commodity Credit Corporation would buy the entire Brazilian coffee quota. “The War Production Board took control of all coffee entering the United States, effectively ending a free market,” says Pendergrast.

As in World War I, coffee beans were sent directly to the front lines. In one Marseilles factory, 12,000 pounds a coffee was roasted per day in roasters built from converted gasoline drums. Brands looking to turn a wartime profit began an arms race to create improved instant coffee.

Instant coffee was invented as far back as the 18th century, but only gained ground during World War I. “The U.S. War Department invested in instant coffee during World I, mainly George Washington coffee. It did the job, but it didn’t taste the best, and postwar consumption fell,” Johnson says.

Nescafé came on the market on April 1, 1938. It tasted closer to traditionally brewed coffee, and the military seized on it. By the time the U.S. formally entered World War II in 1941, Nescafé was inside the emergency rations for every departing U.S. soldier. In one year alone, the U.S. military bought over one million cases, the entire annual output of their U.S. plant. At war’s end, it was included in CARE packages to Japan and Europe.

While American soldiers consumed an average of 32.5 pounds of coffee per person a year, on the home front, most U.S. civilians were making do with just over 8.5 pounds a year—less than a cup a day—thanks to strict rationing. Coffee rationing in the United States began on November 29, 1942, and lasted until July of 1943, though accompaniments like sugar remained rationed as late as 1947. American propaganda presented going with less as a patriotic duty and provided recipes for making meager rations go father.

As Confederate troops had once done, Americans pursued alternatives like brewed chicory or soybeans, though “most Americans were turning to commercially available products like Postum, a grain-based coffee-like beverage developed by C.W. Post.,” says Johnson. (Post, a former patient of 7th-Day Adventist John Hardy Kellogg, was morally opposed to caffeine and positioned Postum as a healthier alternative.)

In the wake of World War II, returning troops wanted their coffee more than ever. It was what was in their cups that had changed. Advances in instant coffee, shifting geopolitics, and military contracts had shrunk the playing field from 3,500 roasters producing coffee for the U.S. market in 1915 to just 1,500 in 1945 (of those, only 57 were major players like Folgers and Maxwell House). It would take the “third wave” coffee movement of the 1990s to re-introduce Americans to the pleasures of artisanal roasting.