Ever since American soldiers encountered heatstroke and lethal dehydration fighting the Germans in North Africa during World War II, scientists and military doctors have studied the debilitating effects of desert heat in an attempt to overcome them.

U.S. Army units regularly engage in simulated combat missions in the Mojave Desert in California. And the Army's Ranger School at Ft. Benning, Ga., the top training facility for the elite unit that produces combat leaders, includes desert exercises.

Acclimatizing troops, developing reliable water supplies and setting up desalinization stations are part of the drill. Diet, uniform, vaccines, hygiene and work codes are designed to keep American soldiers healthy in daytime temperatures that routinely reach 120 degrees in the summer months.

"At this moment, American commanders are waging war against heatstroke and dehydration in Saudi Arabia," said Roger Hubbard, a heat physiologist and director of the heat research division at the U.S. Army Research Institute of Environmental Medicine in Natick, Mass.

Commanders adjust water-replenishment schedules, work/rest cycles and exercise periods according to frequent measurements of humidity, temperature, radiant heat and wind speed. Soldiers sometimes work 45 minutes and rest for 15. At other times, they alternate 30-minute work and rest periods.

Gen. George S. Patton Jr. maintained that a tough soldier could manage in the desert on two quarts of water a day, a regimen that has since been discredited as unscientific -- and potentially dangerous -- machismo. A soldier working an eight-to-12-hour day in Saudi Arabia requires two to three gallons of water or other fluids daily, according to Hubbard. During conditions of continuous battle, troops might need to drink as much as six gallons a day. Suffocating Mission Oriented Protective Posture gear that protects against chemical warfare severely restricts the body's ability to use the evaporation of sweat as a cooling technique. A soldier in full MOPP can lose 1.5 quarts of water per hour. The loss of three quarts without replacement produces fatigue, irritability and loss of appetite.

Army guidelines urge commanders to set up water operations so that re-supply is possible at least once every three hours. Their advice to soldiers: "Hoard water in your body, not in your canteen" or "Better in your belly than on your belt." Troops stationed in Saudi Arabia routinely drink between one and two quarts of water at a time. This "prehydration," according to the Army, improves performance during periods of intense activity.

The cooler the water, the more palatable it is, so soldiers attempt to shield supplies from the sun by shading and insulating 450-gallon water trailers on wheels, called water buffaloes, or by using small mobile coolers.

Eating ice to stave off dehydration is not recommended. Its use has been a major source of intestinal flu in previous wars. Freezing diminishes the level of protective chlorine and enables the surface of the ice to pick up impurities during transportation, especially in a dusty climate. A variety of flavorings increases the palatability of water, but the Army warns that popular commercial flavorings such as Koolaid and Gatorade neutralize disinfectants. Canteens must be thoroughly rinsed following use of these products, and native water and food are off limits.

Weight loss in desert conditions is not regarded as desirable, even for overweight troops.

"Do not permit field deployment to be used as a convenient way of going on a diet," the guidelines for desert survival state. A popular misconception is that food needs decrease in hot weather. In fact, experts say, the actual number of calories required increases in heat, even though studies have shown that soldiers routinely reduce their caloric intake by 20 to 40 percent when they move from the mess hall to eating in the field.

The drop in appetite has several causes, according to Capt. John Moore, a nutritional biochemist for the nutrition division of the Army's Natick, Mass., environmental medicine team based in Natick. Some soldiers don't like the taste of field rations, or MREs (Meals Ready-to-Eat) and have less time to eat them during maneuvers. Soldiers not yet acclimated to a desert environment feel even hotter after eating a meal. Dehydration also curbs appetite; the soldier who is not drinking enough water won't feel like eating either. Army guidelines for desert duty are unwavering: "Soldiers must eat whether they like it or not, whether they're hungry or not."

The perfidy of sand -- which can destroy equipment and cause blinding glare and eye problems -- is well-known among desert warriors. American soldiers in Saudi Arabia are issued sunglasses that have ultraviolet protection.

"Experience has shown that cutting down on eyestrain and dust helps prevent retinitis," or inflammation of the retina, according to the Army's Hubbard. In addition, soldiers exposed to the glare from the sun's reflection off of white sand suffer a form of snow blindness. Ground personnel on airfields wear goggles, as do drivers of trucks and jeeps. As a precaution against nosebleeds, a common problem caused by dry mucous membranes, troops frequently sniff clean water from their canteens.

Desert clothing is not the standard olive drab but a beige khaki uniform made of a cotton-rayon blend that reflects light, provides better camouflage in the sand and allows perspiration to evaporate more easily. Soldiers who handle metal wear gloves, and a floppy desert hat protects against sunburn, as does sunscreen.

The cotton-rayon uniform is not universally popular. GIs including Gen. H. Norman Schwarzkopf, commander of U.S. forces in the Persian Gulf, have complained that it is hotter than the all-cotton ones worn in Vietnam. But Charles Williams, chief of the life support systems division of the Natick facility, says that reaction is "typical of {laymen} who do not understand that a desert environment mandates a different type of uniform from the tropics. Because there is much less humidity, the cotton-rayon material doesn't lie as close to the skin and is more permeable so sweat can evaporate."

Uniforms are reinforced at the knees, elbows and seat to guard against scorching burns, incurred by resting an elbow on the hot metal hood of a jeep, and kneeling or sitting on a hot rock can have painful consequences.

In addition, a reinforced yoke across the back and shoulders of the uniform provides insulation that helps keep the body core temperature at 98.6 degrees. Such insulation is a must when the outside temperature is 20 degrees hotter than that, says Williams. Since the 1970s, the uniform has been tested on troops stationed at various desert military posts in the United States. Army officials say that the uniform also has a better infrared signature, meaning that the wearer is less easily detected by heat-seeking equipment.

Lucretia Marmon is a freelance writer in Chevy Chase.