The United States may have one of the largest armies on earth, but even the Pentagon has taken no chances at being caught off-guard by an unusual foe. In fact, in 2011, the U.S. Department of Defense released a strategy to combat a potential zombie apocalypse. While the potential opponents might be fictional, the military took it seriously. In fact, the first line of the Counter-Zombie Dominance Plan, or “CONPLAN 8888-11,” states, “This plan was not actually designed as a joke.”

The origins of the plan can be traced to training exercises held in 2009 and 2010, during which young officers participating in the Joint Operational Planning and Execution System realized the potential upsides to planning for a hypothetical zombie attack. With roving zombies as the target in these fake scenarios, rather than enemies in real-life potential hotspots like Tunisia or Nigeria, there was a much smaller risk of the plan being taken seriously—or ruffling diplomatic feathers.

And the fantastical idea of battling zombies helped new newcomers think outside the box when it came to devising creative strategies and tactics. As the Pentagon notes, “Our intent was to place this tool ‘into the wild’ so that others who were interested in finding new and innovative ways to train planners could have an alternative and admittedly unconventional tool at their disposal that could be modified and updated over time.”

It also tapped into the growing pop culture fascination with zombies. The first zombie tales date back to 17th-century Haiti, where zombies were believed to be African slaves who had committed suicide and weren’t allowed to pass on and return home. As a result, they would be forced to work on the plantation for eternity. The terrifying—and thrilling—myths surrounding the undead really caught on in the United States with the release of the 1968 film The Night of the Living Dead.

CONPLANN 8888-11 laid out a 31-page strategy in three parts. First, create and uphold a defensive plan to protect humankind from mind-munching predators. Second, establish procedures to eradicate any threat of zombies. Third, restore law and order to a war-ridden economy.

The zombies themselves are classified into eight categories, ranging from your run-of-the-mill undead created through bacteria and pathogens in the air and “evil magic” zombies created by a mystic, unknown source, to vegetarian zombies who eat herbaceous foods to satiate their unending craving for “grains.” Of these eight categories, only one is based in reality. The potential threat of “chicken zombies” originated with a 2006 incident in Petaluma, California, when the unsuccessful euthanizing of poultry using carbon monoxide resulted in haunted hens crawling out the piles of their slain sisters, and walking around until their bodies died of internal organ failure.

Leaving no stone unturned, CONPLAN 8888-11 also includes the possible legal ramifications of attacking zombies. As it turns out, laws prohibiting military violence, both domestically and internationally, are only geared towards human and animal life. So in the case of an invading horde of unknown pathogenic beings, zombies seem to be fair game.

The Pentagon isn’t the only governmental department to use zombies as a learning tool. The Center for Disease Control (CDC) has also played off the popularity of The Walking Dead and other zombie-related cultural phenomena, releasing a zombie preparedness plan to better inform the public of what to do if—or when—a disaster strikes.