It's easy to write off preppers as part of a fleeting, modern phenomenon, born of some kind of post-9/11 panic. But survivalism has some deep roots in American culture, and few recipes have stood the test of time quite like survival bread. What is survival bread, you might ask? Well, the definition of survival bread kind of depends on what type of survivalist you ask. Some believe that survival bread is bread that you can make "even when SHTF," as the writer behind the blog Year Zero Survival explains, when all other food sources have run out and modern civilization as we know it has crumbled. This kind of recipe uses as few ingredients as possible to make a meal that's as hearty as possible, though it generally starts with some combination of flour and water and maybe yeast if you planned ahead.

Other survivalists take a more traditional approach to survival bread and look back into history for inspiration. Over the centuries, survival bread has been known as hardtack, pilot bread, and ship biscuits, among dozens of other names, though the basic premise is the same. It's survival bread that will basically last forever, without refrigeration and regardless of weather conditions. That's why this hard style of biscuit was favored by sailors. In fact, the British Royal Navy started mass-producing these biscuits in the mid-17th century to feed their ever-growing fleet of sailors.

Hardtack really came into its own in American culture during the Civil War. Perhaps the best description of this quotidian ration comes from a 1887 memoir Hardtack and Coffee, or The Unwritten Story of Army Life, written by John D. Billings, a Massachusetts man who served as a volunteer soldier during the Civil War. According to Billings, these hard biscuits were made out of flour and water, and since they were so hard, one of the most common ways to eat them was to dunk the hardtack into coffee. "Probably more were eaten in this way than in any other, for they thus frequently furnished the soldier is breakfast and supper," writes Billings—though the "hardtack and coffee" method of consumption wasn't without risks. "It was no uncommon occurrence for a man to find the surface of his pot of coffee swimming with weevils, after breaking up hardtack in it, which had come out of the fragments only to drown," explains Billings, quickly adding, "but they were easily skimmed off and left no distinctive flavor behind."

If you don't want to make your own hardtack or survival bread, you can buy it. Interbake Foods, headquartered in Virginia, started making Sailor Boy Pilot Bread in 1918, and today, it's likely the only commercially available hardtack in the United States. These bread crackers are especially popular in Alaska, and by some estimates, the vast majority—as many as 95 percent—of Interbake's boxes of Sailor Boy are sent straight to the forty-ninth state.

But part of the appeal of survival bread is that you can make it when SHTF, and really, the basic survival bread recipe is so simple that there's no reason not to learn it, just in case. All you need is water and flour and a heat source and maybe some salt. You can also customize your own survival bread recipe, using ingredients that you already have in your pantry, in case civilization collapsed this afternoon. The folks at Gun Digest, for example, recommend adding some applesauce or beer to your basic survival bread recipe to add some moisture and flavor. And if you really want to get into the prepper spirit, know that you can also bake survival bread in an Altoid tin.