Tyler Hicks/The New York Times

It is an age-old axiom that little creates absurdities like war, and this notion remains evergreen today. Take the case of the two victims of gunshot wounds shown in Tyler Hicks’s photographs, which accompany this post.

Both men were struck by bullets in a gunfight between Marines and the Taliban in Marja on May 29. The first victim, the elderly man, had been shot through the right hip. The Marines assumed he was a civilian. Under NATO rules, when civilians are wounded in any way related to NATO activity, including when they are struck by stray bullets or caught between fighting forces, they are eligible for military medical care.

This man’s wound led to the standard reaction.

The Marine patrol in the firefight called for an Army medevac helicopter, which was located on an airfield to the south. The air crew scrambled. With an escort aircraft trailing behind, a Blackhawk from the 101st Combat Aviation Brigade, with a medic aboard, was soon racing over the desert to Marja. Minutes later, the helicopter landed in a field beside where the fighting had been, and the Marines carried the wounded man, whom they had been treating on the spot, to the aircraft’s open doors, just as if he were one of their own.

With its escort aircraft circling and buzzing the tree lines to suppress any lingering Taliban fighters, the medevac helicopter took off, and began its evasive moves low over the ground, headed to a trauma-care center at Camp Dwyer. But as they flew away from the landing zone, the aircraft’s two pilots, Chief Warrant Officer Deric Sempsrott and First Lt. Matthew E. Stewart, spotted a red plume of smoke rising from another field.

They thought a nearby Marine had been shot, and that his patrol was signaling for help. They banked their Blackhawk into a tight left turn, doubled back and descended toward a field near where they had just picked up the first man.

This was a dangerous move. The longer a helicopter loiters near a fight, the greater its risk of drawing ground fire, either from small arms or a rocket-propelled grenade. The pilots did not hesitate. Soon their aircraft was on the ground. Its escort was buzzing a fast circle around it again.

The crew waited for the wounded Marine. No Marine had been hit.

Tyler Hicks/The New York Times

Instead, a second Afghan, the younger man pictured at right, was led toward the aircraft and helped aboard. He had a gunshot wound, too. The pilots took off again and banked hard, gathering speed and heading to Camp Dwyer once more. Sergeant Ian Bugh, the medic, examined the two men and began to treat them.

Under the rules guiding American troops’ actions in the field, and in alignment with current Western notions of counterinsurgency, this was exactly how civilian casualties were supposed to be handled.

The helicopter landed roughly 10 minutes later, and teams of Navy corpsmen on litter-bearer duty ran out and carried the Afghans to the surgical tent — again, the same treatment that any American service member would get.

The pilots taxied their aircraft to its parking space, and shut the Blackhawk down.

Mission complete.

Then came the twist.

A short while later, after the patients had been evaluated and stabilized, another medic from the Blackhawk detachment visited the hospital to check on the two Afghan men. He found that when a forensic examination had been conducted of the patients’ hands, both men had tested positive for gunshot residue. This meant that in all likelihood they had been firing weapons a short while before. If this was so, then the most likely explanation was this: they had been firing at the American patrol, and after being shot had assumed the role of wounded civilians, seeking help from the same men they had been trying to kill, and from the same helicopters that, each day, the Taliban fighters try to shoot down.

This is the bizarre world of Afghan war, where both sides know the rules and fight according to them. For one side, the rules can resemble constraints. For the other, they can mean opportunity.

NATO’s rules of engagement govern when, where and how force can be used, and in what forms, from a pistol shot to an airstrike. They also guide decisions on when and how Afghan homes can be entered. Rules of eligibility help shape when an Afghan can be given access to the military’s medical system. Other rules determine when an Afghan can be detained, and by whom, and for how long, and where, and under what conditions. Over the years, the rules have shifted repeatedly. No doubt they will continue to change. And whenever a change is made, soldiers and Marines often joke that it seems that the Afghans they fight know the new rules as surely as American troops do, and adjust to them immediately.

This seemed to be the case on May 29 — when, if the soldiers had it right, two Afghans fighting the Americans took a break when they got shot, tossed aside their rifles or machine guns, and chose the wounded civilian option to hitch a ride from their enemy to their enemy’s top-shelf gunshot-trauma care.

How the case ends is anyone’s guess. The medic who checked on the patients said they were being fingerprinted and undergoing iris scans. This meant that they were being logged into the military’s biometric database. This might help identify them, or link to them to crimes or other firefights. But military officers and law enforcement contractors said the Afghan government often does not accept the results of gunshot residue tests as evidence.

Medics and pilots have no say in matters of detention. They are, in a simple sense, a high-risk ambulance service, bound by rules and a propelled by a desire to recover patients from dangerous places in the service of saving lives. They move the patients, an early leg of what is often a patient’s long journey. Other people decide the next steps. After the mission, Chief Warrant Officer Sempsrott accepted the news of the forensic evidence calmly.

“It doesn’t surprise me,” he said, and shrugged.

Dwelling on unpleasant facts serves little purpose, at least for crews that wait beside an airstrip for a call that could come at any time.

One mantra here is this: Put aside the last mission. Be ready for the next, whatever it might bring.