Updated at 4:45 pm on August 30, 2013 with additional information.
To battle the more than 50 wildfires now burning across the western United States—including the massive Rim Fire threatening Yosemite National Park in California—thousands of firefighters have employed a vast arsenal of technology, including hundreds of specialized vehicles.
The effort around the Yosemite wildfire, which has burned more than 284,000 acres and had been just 20 percent contained by Wednesday, has involved 16 helicopters, 49 bulldozers, 454 fire engines, and 39 water tenders, wheeled tankers that transport water.
The 4,000 firefighters battling the Yosemite fire and their fleets of vehicles resemble a small army in more ways than one: many of the tools and techniques firefighters in Yosemite and beyond are using can be traced back to just after World War II, when a surplus of military equipment and trained personnel revolutionized thinking about fighting wildfires. (Related: "New Firefighting Technologies: Drones, Super Shelters.")
The first firefighting air tankers or "slurry bombers," for example, were WWII warplanes whose torpedo bays had been modified to carry tanks that could dump water on fires.
And bulldozers, which modern firefighters use to cut swaths on the ground to prevent flames from spreading, owe some of their current design to the Second World War. "The bulldozer was made significantly better as part of the war effort," said John Fehr, Director of Technology and Development at the U.S. Forest Service.
One big improvement the military made to bulldozers was to install bigger engines that gave them more horsepower. The military also improved the tracks—or treads—that the vehicles use to move around, in place of wheels.
"The military was so much better with tracked vehicles than private industry had been," Fehr said. "They were able to improve the tracks and suspension systems for them, which made it so they could work in steeper and rougher country."
The bulldozers and warplanes donated to the Forest Service by the U.S. Army after World War II started a tradition of surplus equipment donation that continues today.
"One government agency can take surplus property from another and put it to use without having to pay," Fehr said. "An example of that is when our fire engines are replaced, we usually give the old ones to county or local fire departments for them to use."
The military's influence can also be seen in the ranks of firefighters themselves. For instance, parachuting specialized firefighters, known as "smoke jumpers," into remote areas to combat wildfires shortly after they start has become a critical tool in mitigating damage.
"They're usually sent out to fires when they're first detected," Fehr said. "It depends how big the fire is, but they might only put two jumpers onto a fire. But in a remote area where it could take a day to get there by hiking or riding horse, a smokejumper could get there in an hour."
The idea of smoke jumping grew out of the World War II fighting experience. "After World War II, people who had parachuting experience out of the war started thinking how that could be adapted to firefighting," said Fehr.
But not everyone agrees with this version of events. If anything, the reverse is true, and smoke jumpers influenced the training programs developed for aerial troops, said Chuck Sheley, editor of Smokejumper Magazine.
“We were doing steerable parachutes in 1941, long before the military,” Sheley said.
Citing USFS historical records, Sheley says that the first smoke jumping crews were established in 1940—over a year before the bombing of Pearl Harbor that forced the United States to enter the war.
"The forest service started dropping cargo in the early 1930s using parachutes," Sheley explained. "In 1936, someone floated the idea of dropping men in addition to cargo. That idea was overruled at the time, but in 1939 [David Godwin of the U.S. Forest Service] approved an experimental program at Winthrop, Washington. The first actual smoke jumper crews were established in 1940 in Missoula, Montana, and Winthrop, Washington."
Many former military paratroopers did become smoke jumpers after the war beginning in 1946, Sheley said, but the occupational shift wasn't necessarily an easy one.
"I've had to retrain many airborne [soldiers] because there's so many differences between the two jobs," he said. “As smoke jumpers are not combat soldiers, paratroopers are not firefighters.”
Today, smoke jumpers often parachute into the vicinity of budding infernos dressed in little more than padded suits, face masks, and helmets.
As was the case for some troops' weapons during World War II, the smoke jumpers' equipment—like crosscut saws and the "pulaski," a tool that combines an axe and a grubbing hoe—are dropped in separately.
"It's delivered as paracargo," said Keith Windell, the acting fire, aviation, and residues program leader at the Forest Service's Missoula Technology and Development Center in Montana.
Armed just with hand tools, smoke jumpers are sometimes tasked with starting the work of putting out a blaze until reinforcements can arrive.
"They also have the ability to call in air tankers to assist them," said Windell, who used to be a smoke jumper. The jumpers will sometimes clear away trees to create impromptu landing pads for helicopters to ferry in additional firefighters, just like troops might do in a war zone.
Closest Thing to War Fighters
The military and the U.S. Forest Service continue to work together to develop new firefighting technologies and techniques.
"The military found that the firefighting environment is the closest thing they have to test products for war fighters," said Windell.
For example, the parachutes used by both smokejumpers and U.S. Army parachutists have undergone subtle design changes to improve their reliability and maneuverability and to better control their speed of descent as a result of joint tests.
And hydration studies conducted by the Forest Service in 2009 with input from the Army showed that it's important for firefighters to drink water with electrolytes-such as sodium and potassium—during their shifts to replenish those lost through sweat.
"It reduces dehydration," Fehr said. "When people get dehydrated, one of the first things to go is their cognitive abilities. If you can keep their electrolyte levels up, they're going to be thinking more clearly and be able to do more work."
Another recent experiment conducted with the Army's input showed that it's better for firefighters to eat small meals throughout their shifts rather than one big meal beforehand.
"If you can kind of have them graze throughout the day, they're able to do more work, and they stay stronger and more alert throughout the shift," Windell said.
"We find that if properly hydrated and fed, [firefighters] can be 20 to 30 percent more productive in the last third of their shifts, which can last 12 to 16 hours," he said.
As a result, the Forest Service now recommends that a third of the water that on-duty firefighters drink contain electrolytes—and that they carry dried fruit to snack on.
Follow Ker Than on Twitter.