Ken Pimlott once commanded a firefighting army. As the former chief of the world's largest firefighting force, Cal Fire, he had more than 15,000 people and 50 aircraft at his disposal.
But even he concedes that this mighty force is being overwhelmed by the fires burning along the west coast of the United States.
"These fires are growing so large, they require so many resources that are spread so thin … there just aren't enough to deploy around all these fire lines to meet containment, to put the bulldozer lines in, and put crews out to cut fire lines," he said.
Mr Pimlott retired last December after 30 years with Cal Fire, the California Department of Forestry and Fire Protection.
He said what kept him up at night was what will happen when the hot winds of autumn — or fall — arrive.
"The fatigue on firefighters is already significant. But historically our most destructive fires are in October," he said.
"In the fall, northern California has very dry, intense Diablo winds and southern California has Santa Ana winds, which are very similar. So we really have a long way to go."
Five of the 10 biggest fires in Californian history have occurred this season, according to Cal Fire.
Almost 3 million hectares have burnt across the US this year, compared to the 5.7 million hectares of eucalyptus forest estimated to have burned in Australia's 2019–20 fire season — now known as Black Summer.
A black mirror
Mr Pimlott said he saw clear parallels to Australia's Black Summer.
"I do think the fires are spreading under conditions that are very, very similar," he said.
"We've been coming off five years of drought from several years ago. But the state never really recovered.
"Then we had record heat conditions of over 130 degrees [Fahrenheit, or 54.4 degrees Celsius] in Death Valley down in south-eastern California about a month ago.
"That just created a tinderbox that was ready to ignite."
Australian fire scientist Owen Price from the University of Wollongong echoed Mr Pimlott's comparison.
"There's a very strong climate change signal here," Dr Price said.
"Parts of New South Wales and Victoria were experiencing their deepest drought on record since records began in the early 1900s. And there were certain days in New South Wales that broke the temperature records during these fires, and also fire danger records.
"I think you can say there's a similar trend going on in the western US."
The Bureau of Meteorology (BOM) wrote in its 2018 State of the Climate Report that:
"There has been a long-term increase in extreme fire weather and in the length of the fire season across large parts of Australia since the 1950s."
Similarly, the US Government's Global Change Research Program wrote in its 2017 Fourth National Climate Assessment that:
"The incidence of large forest fires in the western United States and Alaska has increased since the early 1980s [high confidence] and is projected to further increase in those regions as the climate warms, with profound changes to certain ecosystems."
Professor Andrea Thode from Northern Arizona University's School of Forestry said record dryness was a major factor in the severity of the US fires.
"We know that vapor pressure deficit [VPD], a measure of vegetation water stress, has been tied to high severity fire in the western United States," she said.
"Higher values of VPD mean the vegetation is drying out. In California, VPD was setting records in August.
"So the higher temperatures meant higher VPD, which created very dry vegetation. It was a matchbox waiting to be lit."
BOM said in a statement that in the spring and early summer of 2019, exceptionally low or record-low relative humidity was observed at a number of locations in Australia where fires occurred.
"This includes very low overnight humidity, which can be significant, in that cooler temperatures and higher relatively humidity can act to subdue fires overnight," it said.
According to Dr Price of UoW, really hot, dry, windy weather in Australia and the United States had created fires that were essentially unstoppable.
"There are definitions of fire intensity. For example, at 4,000 kilowatts per metre you cannot put fire crews in front of a fire," he said.
"At 10,000 kilowatts per square metre you can't really stop them with water bombing.
"That intensity measure is easily exceeded in some of these fast-running fires that can be 10 times more intense than those limits."
Mr Pimlott said under those conditions business-as-usual strategies no longer worked.
"We really have to rethink if we're going to sustain this firefight all summer," he said.
"We really have to rethink the fire suppression side. Because it's definitely more complex and requiring many, many more resources than ever before."
Australian fire scientist David Bowman from the University of Tasmania was more blunt.
"The 'total war on fire' strategy has been lost," he said.
"Continuing investment in fire suppression with bigger and bigger aircraft, more aircraft — it looks fantastic, but it's a fantastic way to drain budgets. It's extremely difficult to sustain.
"I would suggest that this season is probably the US's Waterloo with total war on fire and fire suppression."
Arguments rage over climate change, fuel loads
In California, Donald Trump recently blamed the fires on forest management.
"When trees fall down after a short period of time, they become very dry — really like a matchstick … and they can explode," the US President said on Monday as he surveyed the damage.
But unlike Australia, there is much broader agreement in the US that forests need to be more actively managed.
NAU's Professor Thode said there needed to be more prescribed burning and thinning of forests.
"We need to be using wildfire during the shoulder seasons, and in the times where it's not the worst-case scenarios, to promote healthy fires moving through our ecosystems," she said.
"It is currently happening. But it's not happening anywhere on a scale that I think anyone is satisfied with — including the managers themselves."
Professor Bowman said the US was already looking at Australia as a leader in fuel load management.
"In Australia, our approach has been more trying to manage fires with burning, and using fire to create natural firebreaks, to change the behaviour of fires," he said.
"In America it's total war on fire — a massive firefighting air force and army that is highly trained."
Professor Bowman said both of those strategies had been proven to work.
"The problem is they just don't work when you rapidly warm the climate. So the Americans look to us and we look to them. It's like a ping pong game," he said.
Professor Thode was worried about what might come after the US's worst ever fire season.
"We may look back in 20 years and go 'Boy, wouldn't it be nice to have a year like 2020?'" she said.
"Because if we continue on the path that we're on, this really could be much more of a normal year instead of an extreme year.
"It seems like every year we say that. That future is pretty scary."ABC