(CNN) -- Even the prospect of rain is little help to the crews fighting an Arizona wildfire that killed 19 of their comrades.
But firefighters battling the Yarnell Hill blaze did get a boost from the U.S. military, which committed four specially equipped C-130 transports to the effort Tuesday. About 400 ground personnel and 100 incident management staff are working to control the fire, shadowed by the near-total loss of an elite team that was overrun by the spreading blaze Sunday.
"You have to acknowledge it," Karen Takai, a spokeswoman for the firefighting effort, told reporters Tuesday morning. "You can't push it behind in your head, but acknowledge it, and then they get their head back in the game. They have to focus very hard on the ground, or we'll be in that same circumstance again."
The fire had scorched about 8,400 acres Tuesday morning and was largely unchanged Tuesday afternoon, incident commander Clay Templin told a public meeting.
The region has been suffering from an extreme drought, and the winds whipping through the mountains can blow embers into new patches of parched woodland and mesquite grass, Takai said.
"That mesquite is extremely oily, and once that starts, an ember gets into those extremely dry fuels, that fire is going to rip," she said. "It's very difficult to control at that degree, especially with the winds that we're having out here."
The fire has scorched about 13 square miles of the mountains outside Prescott, 80 miles northwest of Phoenix. Late Tuesday, the blaze was 8% contained.
Earlier in the week, the Yavapai County Sheriff's Office advised residents in the communities of Peeples Valley and Yarnell to evacuate their dwellings. An estimated 200 homes and other structures have burned in Yarnell.
Though firefighters got a break with higher humidity and brief showers Tuesday morning, "The winds are just drying out that fuel right after the rain is hitting the ground," Takai said. "It's a pattern that is very difficult to work with."
The C-130 crews now joining the fight will have their work cut out for them in battling what is now considered the deadliest fire in state history.
Equipped with the Modular Airborne Fire Fighting System, or MAFFS, the planes, loaded with water or fire retardant, can drop 3,000 gallons in less than five seconds. The retardant covers an area a quarter-mile long and 60 feet wide, and the aircraft can land, reload and be airborne again in under 20 minutes.
"They'll be capable of actually dropping a lot of liquid on that ground in areas where it will be most effective," Takai said.
The planes are from Colorado, where crews had been working on fires for the last several days. But they are now considered more vital for Arizona. The military deployment is coming at the request of civilian firefighting authorities.
A Defense Department official confirmed the details to CNN but declined to be identified because an announcement has not yet been made.
CNN's Barbara Starr contributed to this report.