It is a peculiar fact of an Afghan war that friends become enemies and suddenly friends again, always knowing that either one would have killed the other if they'd had the chance.
This constant shifting of alliances has long been Afghanistan's curse but may yet turn out to be its blessing. It is crucial to understanding why the anti-Taliban forces, an alliance of warlords, heading for defeat less than two months ago, is now suddenly in the capital, Kabul.
On the main road linking northern and southern Afghanistan through the Salang Pass, Taliban and opposition forces were in a stand-off until 2 a.m. yesterday, when two foes decided to revive a friendship that began more than 15 years ago.
Twelve hours later, former Taliban commander Mohammed Aman Abed was leading 50 of his men up the Salang Pass, over which they had fought so bitterly for years.
They were heading to the front line north of Kabul to fight the Taliban force from which they had just defected.
Abed (24) and Del Aqa (36) rode side by side on horseback as the defeated Taliban soldiers turned opposition fighters trudged along behind.
One pulled the commander's sheep along by a cloth tether. Another carried the commander's canary in a cage, gingerly stepping past a Taliban land-mine, left exposed in a pothole in the middle of the road.
They were men from different parts of Afghanistan, driven by loyalty to a new battle front, and none found it the slightest bit strange that people who were trying to kill each other before sunrise were now marching off to war together as the sun set behind the mountains.
Aqa, the opposition Northern Alliance's second-in-command in the strategic Salang Pass, found it a little offensive that a visitor would ask how Afghan enemies could be allies so easily.
"Don't think us so simple," Aqa said, and he smiled wryly.
Then he gestured toward a series of reinforced concrete bunkers, where fleeing Taliban fighters left behind heavy machine guns, anti-tank weapons and ammunition that will soon be turned against other Taliban soldiers.
"We made these bunkers during the fighting against Dostum," Aqa said proudly. He was referring to one of Afghanistan's most notorious turncoats, Abdul Rashid Dostum, a general under the Soviet-backed government who then switched to the mujahideen factions that in 1992 overthrew President Najibullah.
In January 1994, Dostum joined forces with mujahideen warlord Gulbuddin Hekmatyar and turned against interim president, Burhanuddin Rabbani, setting off a vicious civil war in Kabul that killed about 50,000 people and reduced much of the city to ruins before the Taliban seized the capital in 1996.
Dostum is now back with the Northern Alliance and on Friday helped to retake the northern city of Mazar-e-Sharif, his longtime fiefdom.
As Abed and his former Taliban fighters headed toward the Kabul front, the Northern Alliance claimed that the defection of hundreds of other Taliban soldiers defending the city helped the opposition make rapid advances in an offensive launched that morning.
Like Abed, the fighters were mainly local commanders and their soldiers who joined the Taliban five years ago as the fundamentalist Islamic movement made stunning advances across Afghanistan to seize Kabul. The defectors were simply joining the winning side again.
Abed and his 600 soldiers were weak links in the Taliban chain and had been for a long time.
He is a Tajik, born in the rugged Salang, as is Aqa, and the commanders' ethnic and family ties proved stronger than loyalty to the mainly ethnic Pashtun Taliban movement.
Aqa met Abed when the latter was a child, during visits to the home of the boy's brother-in-law, Aqa Sherin, who was once a famous commander of Northern Alliance troops in Parvan province, north of Kabul.
Abed secretly contacted Del Aqa a year ago to discuss returning to the anti-Taliban opposition.
"We wrote letters and they sent messages through the radio," Aqa said.
But Abed didn't decide to make his move until Sunday night, after weeks of US airstrikes had improved the Northern Alliance's fortunes. Abed was reluctant to talk about how the deal was worked out because he was only able to bring 600 of his men with him and fears Taliban commanders will take revenge against those he left behind.