This U.S. soldier boots were the last on the ground in Afghanistan

Sometime before 11:59 p.m. Monday, he ascended the ramp of a C-17 transport plane with Ross Wilson, the top diplomat in Kabul, officials said, closing the chapter on U.S. involvement in the country's longest war.

Images of Donahue, awash in night-vision green, may become an enduring memory of the end of the U.S. war in Afghanistan, a 20-year effort that began with toppling the Taliban government and ended with the militants parading onto the airfield soon after the general left. The photos are uncannily symmetrical to some of the earliest depictions of U.S. operations in Afghanistan, including blurry night-vision green videos of Army Rangers jumping onto an airfield a month after the Sept. 11 terrorist attacks.

The images are also reminiscent of how the war looked from the perspective of U.S. troops fighting across two decades, often under cover of darkness. Pilots and aircrews watched the rugged terrain in Afghanistan unfold underneath them in hues of green and black, and commandos on nighttime raids searched for targets with the beams of their rifle-mounted infrared lasers, visible only through night-vision devices.

Donahue's departure capped his own involvement in a military effort that began soon after hijacked planes crashed into the World Trade Center. As a young aide, Donahue was assigned to the Pentagon but was on Capitol Hill with Air Force Gen. Richard Myers, vice chairman of the Joint Chiefs of Staff, as the attack unfolded, according to Military Times.

He later went on to command a squadron of the secretive Delta Force counterterror unit in Afghanistan, Military Times reported.

For this month's emergency evacuation mission, Donahue oversaw security at the Hamid Karzai International Airport, where U.S. troops marshaled in thousands of Afghans and U.S. citizens for emergency flights out as defense officials warned of likely attacks. The intelligence proved grimly accurate. A suicide bomber killed at least 170 Afghans struggling to escape on Thursday, along with 13 U.S. troops charged with searching and processing evacuees at an airport gate.

The photos of Donahue's departure from the country is poised to join some of the most memorable images from the U.S. effort.

In one image, an unnamed paratrooper from the 82nd Airborne Division has a face of exhausted determination during a 2002 mission to find a weapons cache somewhere in southeastern Afghanistan.

The U.S. effort continued for years afterward, even as it was overshadowed by the war in Iraq.

Attention turned back to Afghanistan in 2008, when heavy combat escalated in the fight to retake Helmand province in the south. In one photo, Marine Sgt. William Olas Bee takes cover as Taliban fire sends pieces of a mud wall tumbling through the air.

The next year, as U.S. forces were positioned in the eastern mountains to thwart militants crisscrossing the border with Pakistan, a firefight erupted in Konar province, rousing soldiers from sleep at a remote outpost. That included Army Spc. Zachary Boyd, still in his underwear and flip flops.

"He immediately grabbed his rifle and rushed into a defensive position clad in his helmet, body armor, and pink boxer shorts that said 'I Love New York,'" Defense Secret Robert Gates said after photos of Boyd were printed in newspapers around the world.

"Unfortunately, or fortunately, depending on your perspective, an AP photographer was there for a candid shot," he said, according to NBC News.

The closing images of the war, shot from inside a C-17 with Donahue as a subject were much more subdued. Donahue walked up the ramp as the lights of the Kabul airport were lit behind him.

A short time later, Taliban members took the airport by force, according to video posted on Twitter by a Los Angeles Times reporter walking with the militants as they inspected U.S.-supplied helicopters. The aircraft and other vehicles left behind were decommissioned by departing troops, the Pentagon said.

The insurgents certainly had the ability to watch Donahue's flight depart. The armed men in the hangar wore their own night-vision goggles atop their helmets - a small part of the bounty of U.S.-supplied equipment they now claim.