KABUL — Heavy fighting between Afghan security forces and Taliban militants is taking its toll, as large numbers of casualties across the country are pushing recently trained Afghan air medical evacuation crews to their limits.

During one week in August alone, between Aug. 22 and 29, Afghan crews recovered 125 Afghan troops killed and more than 280 wounded, according to U.S. military documents reviewed by The Washington Post on Thursday. The casualties — equating to almost 18 dead per day — were spread across 37 different locations all over the country. By comparison, the worst month for U.S. forces was August 2011, when 71 were killed.

The snapshot of the Afghan dead and wounded – tracked closely by the U.S. military – helps illustrate the staggering casualty numbers that increasingly weigh on top U.S. generals, given what they say about the state of the war in Afghanistan 15 years after American forces first toppled the Taliban and the Afghan security forces’ ability to keep fighting an entrenched insurgency.

The documents reviewed by The Post contained figures tracked by U.S. troops responsible for advising the Afghan air force medical evacuation crews. Thus, the actual number of dead and wounded could be higher as the documents only pertain to those casualties lifted out by air.

According to the documents, the Afghans performed 118 total air evacuation missions — the majority of which were with their aging fleet of Russian Mi-17 helicopters and C-208 Cessnas — between Aug. 22 and 29, recovering 288 patients and 125 human remains.  A U.S. officer familiar with the documents confirmed that the 125 human-remains figure refers to those Afghan security force members killed in combat during that time.

Afghan airborne casualty evacuation missions have spiked since 2015, according to a Pentagon report, released in June 2016, assessing the state of the Afghan military. From Jan. 1 to April 1, there were 2,727 air casualty evacuation missions, up from 1,944 missions during the same period in 2015.

“Although [the Afghan military] continues to prioritize [casualty evacuation missions] … requests far exceed available capacity,” the report says.

The officer, who spoke on the condition of anonymity to discuss statistics that had not been made public, said the Afghan air evacuation activity was roughly consistent from week to week. However, the casualty numbers fluctuate depending on the time of year. The spring and summer months — known as the “fighting season” — often see a spike in casualties as the warmer weather brings an increase in Taliban activity. The casualties, he said, suffered from a mixture of wounds, namely, improvised explosive device blasts and gunshots.

Unlike some of the Afghan troops that are buoyed by U.S. and coalition support by way of advisers and airstrikes, Afghan air medical evacuation personnel receive only minimal direct support on their air evacuation missions. U.S. medical crews located in the country largely stopped evacuating Afghan troops in early 2015, the officer said. Only rarely do U.S. advisers help with battlefield evacuations, instead sticking to training and “capacity building,” he said.

“The amount of missions these guys are doing is a lot even by U.S. standards,” he said, adding that 40 Afghan air medics — with training ranging from ad-hoc EMTs to physician assistant levels — are responsible for caring for and recovering the majority of wounded Afghan security personnel.

The Afghan security forces’ blossoming casualty numbers have been a sticking point for the top U.S. generals charged with overseeing the war. Last week, the chairman of the Joint Chiefs of Staff, Marine Gen. Joseph F. Dunford Jr., told lawmakers that the Afghans have “taken far more casualties than we are comfortable with” and that the war in Afghanistan was a “stalemate.”

On Friday, the top U.S. commander in Afghanistan, Army Gen. John Nicholson, echoed Dunford’s concern during a news conference at the Pentagon but would not provide specifics on the number of Afghan soldiers killed and wounded. In August, however, Nicholson said more than 900 Afghan security forces had been killed in July.

August saw heaving fighting between Afghan forces and a resurgent Taliban. In the country’s southern Helmand province, the birthplace of the Taliban and a hub for the global opium trade, insurgent forces came within miles of the provincial capital of Lashkar Gah. On Aug. 23, an Army Special Forces soldier, Staff Sgt. Matthew V. Thompson, 28, was killed there when he stepped on improvised explosive device while fighting alongside his Afghan counterparts. In the northeast, Afghan troops spent much of August defending the city of Kunduz, an urban center that briefly fell to the Taliban last fall before it was retaken by U.S. and Afghan Special Operations forces.

Afghanistan’s military has about 300,000 troops, but a lack of political will, corruption and poor leadership has allowed the exponentially smaller Taliban to take back significant chunks of ground since U.S.-led combat operations ended in the country in 2014.

There are 9,800 U.S. troops in Afghanistan. In July, after assessing the country’s deteriorating security conditions, President Obama announced that 8,400 U.S. troops would remain into 2017, a far larger number than the small contingent of counter-terrorism forces that was originally set to remain post-2016.