On the evening of April 5, a pilot settled into a leather captain’s chair at Creech Air Force Base in southern Nevada and took the controls of a Predator drone flying over one of the most violent areas of southwestern Afghanistan. Minutes later, his radio crackled.

A firefight had broken out. Taliban insurgents had ambushed about two dozen Marines patrolling a bitterly contested road.

The Air Force captain angled his joystick and the drone veered toward the fighting taking place half a world away. He powered up two Hellfire missiles under its wings and ordered a crew member responsible for operating the drone’s cameras to search for enemy fighters.

It didn’t take long. Three figures, fuzzy blobs on the pilot’s small black-and-white screen, lay in a poppy field near the road.

“Hey now, wait. Standby on these,” the pilot cautioned. “They could be animals in the field.” Seconds later, tiny white flashes appeared by the figures – the heat signature of gunfire. “There they are,” he said, now sure he was looking at the enemy.

At an Air National Guard base in Terre Haute, Ind., an intelligence analyst whose job it was to monitor the video to help prevent mistakes on the mission also observed the muzzle flashes — but noticed that they were firing away from the embattled Marines.

Marines at Patrol Base Alcatraz, 12 miles from the firefight, watched their screens too. It would be their decision whether to call in a missile strike.

Seconds after the pilot reported the muzzle flashes, the Marines at Alcatraz ordered that the Predator be prepared to strike if the shooters could be confirmed as hostile. At 8:49 a.m., 29 minutes after the ambush began, they authorized the pilot to fire.

In minutes, two Americans would be dead.

LIFE-AND-DEATH CONSENSUS

In addition to the platoon taking fire that morning in Helmand province’s Upper Sangin Valley, the mission involved Marine Corps and Air Force personnel at four locations: Marines of the 2nd Reconnaissance Battalion at Alcatraz, the drone crew in Nevada, the analyst in Indiana and a mission intelligence coordinator at March Air Reserve Base in California.

Senior officers say drone technology has vastly improved their ability to tell friend from foe in the confusion of battle. But the video can also prompt commanders to make decisions before they fully understand what they’re seeing.

In February 2009, a crew operating a drone over Afghanistan misidentified a civilian convoy as an enemy force. The Predator pilot and the Army captain who called in the airstrike disregarded warnings from Air Force analysts who had observed children in the convoy. At least 15 people were killed.

Adding layers of personnel like the analyst in Indiana to cut down on errors also comes at a price: It may slow down the decision to strike when American lives are at risk.

The 2nd Reconnaissance Battalion operated in one of the most violent parts of Afghanistan, an area where drones patrolled virtually nonstop. It had recently revised its procedures to speed up Predator strikes, seeking to prevent “delay of missions by injection of comments” from the Distributed Ground System — military terminology for analysts like the one in Indiana.

THE EMBATTLED PLATOON

The embattled platoon was part of the Lone Star Battalion, a reserve unit based in Houston.It arrived in Afghanistan in early March of this year. Its 2nd Platoon was sent to Patrol Base Alcatraz.

Lt. Christopher Huff, a 24-year-old on his first combat tour, and his Texas reservists were given dangerous duty: patrol Route 611, one of the country’s most heavily mined roads.

Among the platoon’s veterans was Staff Sgt. Jeremy D. Smith, 26, who had served three tours in Iraq and who volunteered to go to Afghanistan. Another volunteer was Benjamin D. Rast, 23, of Michigan, a burly Navy hospitalman on his first tour.

The morning of April 6, Huff, Smith, Rast and the rest of the platoon left Alcatraz about 7:20 a.m. in four armored trucks, heading north. After half an hour, a bomb exploded beneath the third vehicle, but it caused minimal damage. Huff ordered part of the platoon to search the road for more bombs. Seven others, including Smith, Rast and a sniper squad, were sent west of the road to guard against an ambush.

As Smith and his team crossed a field, shots suddenly crackled in their direction. The men dropped to the ground and fired toward some buildings to the west.

THE TECHNICAL SIDE

At the Air National Guard base in Indiana, the Air Force analyst watched the battle unfold on the drone’s video feed. Like the drone pilot, the analyst in Indiana saw three men and muzzle flashes. The analyst typed “3 friendlies in FOV,” meaning three non-insurgents in the camera’s field of view.

A second later, he wrote “Pers are shooting W,” meaning they were firing west, away from the Marines on the road. He sent the fragmentary reports to March Reserve Air Force Base in California, his communications link to the drone crew.

Almost immediately, the analyst had doubts. “Disregard,” he wrote, followed by “Not friendlies,” followed by “unable to discern who pers are.” But he was certain of one thing: The shots were aimed away from the Marines.

Receiving his message, the mission intelligence coordinator and a trainee were dubious. They thought the shots were aimed east toward the Marine convoy. The trainee messaged the Indiana analyst to “double check” his coordinates — and didn’t relay the information to the drone crew.

As debate about the direction of the gunfire continued over the chat system, the analyst did not have access to radio traffic indicating a strike was imminent.

And as he was preparing to strike, the Predator pilot was unaware of the analyst’s doubts.

The missile exploded almost on top of Smith. Other Marines rushed to try to save Rast, who was five yards from Smith. They couldn’t save him.

The first friendly-fire deaths known to have been caused by a drone attack raised broad questions: How did the battalion’s new rules for handling Predator strikes affect the decision to strike? Was the missile fired too quickly? Did the system built to help commanders make better decisions break down again?

The Pentagon investigation’s 381-page report placed much of the blame on Huff, maintaining that up until the moment the missile was fired, he could have called it off. However, it said the deaths were due to “miscommunications,” and that no one was “culpably negligent or derelict in their duties.”