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All over the world, scientists are experimenting on soldiers to keep them awake beyond the limits of normal endurance. Researchers are engineering, and militaries are deploying, chemically enhanced troops. Of all the superpowers we’ve imagined, the one that has turned out to be most attainable—so attainable we’re already using it—is the ability to go without sleep.

Much of this research, which focuses on a drug called modafinil, is openly sponsored and supervised by military agencies. The United States leads the pack, conducting experiments through its Air Force Research Laboratory, Army Aeromedical Research Laboratory, Army Medical Research and Materiel Command, Walter Reed Army Institute of Research, and Special Operations Command Biomedical Initiative Steering Committee. Other countries’ armed forces are studying the same drug: Defense Research and Development Canada, China’s Second Military Medical University, the Netherlands Ministry of Defense, South Korea’s Air Force Academy, Taiwan’s National Defense Medical Center, and the Bioengineering Laboratory of Singapore’s Defense Medical and Environmental Research Institute. India is investigating modafinil through its Institute of Aerospace Medicine and Defence Institute of Physiology and Allied Sciences. France’s research program includes its Ministry of Defense, Military Health Service Research Center, and Institute of Aerospace Medicine. Many of the supervising agencies sound Orwellian: Human Effectiveness Directorate, Fatigue Countermeasures Branch, Département des Facteurs Humain. This, mind you, is just the published research. God knows what’s going on in secret.

The publicly reported studies have tested modafinil in Black Hawk helicopter pilots, F-117 fighter pilots, French paratroopers, and Canadian reservists, among others. They’ve simulated A-6 Intruder bombing missions, AWACS flights, and French Navy patrols. In nearly every trial, modafinil has extended the ability to function without sleep. And we’re already using it in the field. The United States has given modafinil to Air Force personnel since the 2003 Iraq invasion. By 2004, the British Ministry of Defense had bought 24,000 tablets. By 2007, France was routinely supplying it to fighter pilots.

Why has functioning without sleep, unlike other fantasized human enhancements, become real? Because the immediate goal is modestly defined, demonstrably achievable, and easy to measure in experiments. We don’t have to keep you awake forever. We just have to compensate, partially and temporarily, for the cognitive impairment caused by your lack of sleep. In a way, we aren’t enhancing your performance. We’re just raising it back to your normal level—the level at which you function when you’re wide awake. The published experimental reports propose to “sustain,” “maintain,” or “restore” what they call “baseline,” or “pre-deprivation” performance. They aim to “attenuate,” “alleviate,” or “reverse” the “deficits,” “decrements,” and “degradations” caused by sleep deprivation. They speak of modafinil as a “countermeasure” to the “negative effects” of long shifts.

Why are armed forces leading this research? Because they feel the greatest urgency. For an airline or freight company, failure to complete a flight means financial losses. For an air force, it means casualties. In civilian life, you can schedule reliable overnight rest or naps. In war, you can’t. Maybe you’re alone in a cockpit. Maybe you’re on a 12-hour mission requiring constant vigilance. Nobody’s around to take the next shift. Even if somebody were, how are you supposed to sleep in the chaos of combat?

Soldiers have been using stimulants forever. The British downed tea. The Prussians tried cocaine. Nearly every army has leaned on coffee or tobacco. In World War II, both sides took amphetamines. The U.S. military officially approved amphetamines in 1960. Since then, we’ve employed them in Vietnam, Panama, Libya, and during the first Gulf War. Today, all four branches of the U.S. armed forces authorize the use of dextroamphetamine under specific conditions. The Army rations caffeine gum, and every survey suggests that most U.S. aircrews, when in action, use stimulants.

Against this background, modafinil represents a refinement, not an amplification. In 1989, at a defense conference in Europe, a French scientist proposed it for military use. Researchers from the U.S. Air Force Human Systems Division took note and recommended further experiments, based not on the drug’s power but on its precision. Compared with amphetamines and caffeine, modafinil has shown less addictiveness, less cardiovascular stimulation, and less interference with scheduled sleep. Military-sponsored studies have focused less on demonstrating modafinil’s efficacy than on narrowing the effective dose and averting side effects.

In their papers, these researchers never talk about superhuman warriors. They stress a conventional objective: saving lives. They point to fatal accidents and mission failures, including friendly fire incidents, caused by sleep deprivation. Exhaustion kills.

That’s where the logic of enhancement begins. What used to be normal—needing eight hours of sleep each night—is now understood as a fatal flaw. An Israeli report, “Psychostimulants and Military Operations,” examines this “human-machine conflict,” lamenting, “Although an aircraft can mechanically function effectively throughout long hours, pilots cannot.” Canadian defense scientists also highlight this “discrepancy between human need and technological capability.” A U.S. Air Force document warns of disastrous “sleep attacks”—exhausted personnel nodding off on the job. We are the defect. We must be cured.

The cure began with stimulants. Then it expanded to combinations: hypnotics to induce sufficient sleep before your mission (currently approved and administered by all branches of the U.S. armed services), followed by stimulants to switch you back on. The initial idea was to keep you awake for a few extra hours. But the experiments have grown more ambitious, testing drugs for 40, 60, or even 90 hours without sleep. In journal articles, scientists have speculated that with modafinil, troops might function for weeks on just four hours of sleep a night.

Next comes the doping of fully rested troops. “Even in situations where soldiers do receive enough sleep,” says a 2010 report from the U.S. Army Aeromedical Research Laboratory, “they may not be able to maintain appropriate levels of vigilance during long periods of overnight duty without some form of assistance.” This drug treatment can be justified as therapeutic, according to the army lab, since combat is an inherently “abnormal environment,” imposing “extreme conditions” that “degrade optimum duty performance” and “increase soldier risk.” The report points out that “the military has long facilitated (indeed, mandated) pharmaceuticals such as immunizations and prophylaxis in healthy soldier populations where the threat is clearly identified, the risk is unacceptable, the science is sound, the drugs are safe, and the fighting force must be protected and sustained. In the case of cognitive enhancement, for example, one may characterize the threat as an intrinsic agent such as fatigue from necessary sustained combat operations.”

Once we head down this road, there’s no turning back. With multiple countries investigating military modafinil, staying awake becomes an arms race. A report by the U.S. Air Force Research Laboratory explains why: “Forcing our enemies to perform continuously without the benefit of sufficient daily sleep is a very effective weapon.” To win this war of exhaustion, we must “manage fatigue among ourselves.” We must drug our troops to outlast yours. You, in turn, must drug your troops to keep up. On the battlefield of the future, there is no sleep but death.

Read more from Slate’s Superman package: Everyday technologies that already give us superpowers. Is human enhancement cheating? Would you use superpowers for good or evil? Manimal rights: human-animal hybrids and chimeras. We may superpower the immune system to fight cancer and other diseases. The science of choosing the perfect mate. How are extreme athletes able to run 100 miles at a time?