At least 17 US troops have died of heat exposure during training since 2008, while a rising number of military members have fallen ill because of torrid temps over the same period, according to a new report.

Those who died are among the most extreme examples of how rising temperatures from climate change pose a threat to troops in the US and abroad, according to NBC News, which spent nine months probing heat deaths and illnesses in collaboration with InsideClimate.

Reporters interviewed current and former troops, visited two military installations in the Southeast, reviewed reports on deaths obtained through the Freedom of Information Act and analyzed 10 years’ worth of data related to heat illnesses across the US military.

The probe found that despite acknowledging the risks of climate change, the military struggles to adopt a comprehensive strategy for how to train in sweltering conditions.

The military’s investigative reports, often heavily redacted, show evidence of disregard for heat safety rules that led to deaths, as well as a poor level of awareness of the perils of heat illness and the decisions of hard-charging commanders, according to NBC News.

In 2008, 1,766 cases of heatstroke or heat exhaustion were diagnosed among military service members, according to military data. By 2018, that number had jumped to 2,792, an almost 60% hike.

All branches of service saw a spike in heat-related illnesses, but the problem was most significant in the Marine Corps, which saw the rate of heatstrokes more than double during that decade, according to military data.

Health impacts from heat have already cost the military almost $1 billion from 2008 to 2018.

The warming planet “will affect the Department of Defense’s ability to defend the nation and poses immediate risks to U.S. national security,” according to a recent Department of Defense report.

The tendency to continue training despite scorching weather is derived at least in part from the belief that troops must be hardened to withstand the realities of combat, the reporters found.

Current and former defense officials and officers said they were revising guidelines for assessing heat risks, updating prevention measures, refining medical treatment and developing new equipment and technology to keep troops cooler.

Heat injuries “are among the most vexing environmental problems the military faces,” said retired Lt. Gen. Eric Schoomaker, who sounded the alarm on the heat issue as the Army surgeon general almost 10 years ago.

“Almost all are preventable with the appropriate command emphasis and support for troops,” he said, adding that “none need to be fatal.”