Fire managers from New Zealand and Australia have answered calls to help tackle Washington state's wildfires which have burned into the record books.
They joined a ground campaign led by firefighters from across the West and augmented by US soldiers.
The flames that claimed the lives of three firefighters, injured four others and burned 200 homes also inspired an outpouring of volunteers who have been invited for the first time in state history to help battle the blazes.
This summer's fire response across the West has been overwhelmed by destructive blazes tearing through the tinder-dry region.
The biggest fire burning on Monday was in Okanogan County on the Canadian border, where a group of five fires raging out of control became the largest in state history, scorching more than 400 square miles, said fire spokesman Rick Isaacson.
Lightning-sparked fires broke the state record, surpassing blazes that destroyed more than 300 homes in the same county last year.
"I'd like to set some different records," Okanogan County Sheriff Frank Rogers said.
The US is in the midst of one of its worst fire seasons on record with some 11,600 square miles scorched so far. It's only the sixth-worst going back to 1960, but it's the most acreage burned by this date in a decade, so the ranking is sure to rise.
Thirteen firefighters have died nationwide this year, including the three in Washington state who were killed when they tried to escape the fire in a vehicle, crashed and were overrun by flames.
So many fires are burning in the state that managers are taking extreme measures, summoning help from Down Under and 200 US troops from a base in Tacoma in the first such use of active-duty soldiers in nine years.
Jim Whittington, a Bureau of Land Management spokesman in Portland, Oregon, said military assets cannot be used against wildfires until all civilian resources are deployed.
Nearly 4,000 volunteers also answered the state's call for help, far more than will be accepted, said state Department of Natural Resources spokesman Joe Smillie.
The state is looking for former firefighters or heavy equipment operators who can bulldoze fire lines to corral the blazes and keep them from spreading in mountainous, timber-covered areas. So far, about 200 people with the right experience have been cleared to work.
The 70 firefighters from Australia and New Zealand who arrived at the National Interagency Fire Center in Boise, Idaho, were being outfitted to fill a critical shortage of mid-level fire managers such as equipment bosses, strike team leaders and supervisors.
The Southern Hemisphere nations have been partners with the US for more than 50 years, able to lend out firefighters because the severest part of their fire seasons occur at opposite times of the year.
Chris Arnol, international liaison for Australia and New Zealand firefighters, said at a news conference in Boise the firefighters will be ready for the mountainous terrain in the Pacific Northwest.
Warren Heslip, a 47-year-old firefighter from Southland, New Zealand, said the new arrivals were ready for the conditions.
"We're used to tall timber and steep territory," he said.
In Southern California, crews used snow-making cannons to blow water, and planes dropped fire retardant on a 100-acre wildfire burning near the popular Snow Summit ski resort in Big Bear Lake. They were able to build a perimeter halfway around the blaze, but hundreds of homes remained threatened in the mountainous area about 100 miles east of Los Angeles.