The young men -- two Pakistanis and an Afghan -- were captured after a fierce five-hour battle in Paktika province on Tuesday, just a few kilometres (miles) from the border.
During the battle, 24 of their fellow fighters were killed. The bloodied and broken bodies were later shown to reporters by the Afghan army at a base in Barmal district.
The dead were mostly Afghans but included an Arab, Chechens, Pakistanis, Turks and a man from Yemen, an officer said, citing information from the captured three, identity cards and, in one case, a name on a bullet belt.
"Clerics were preaching to us that we are obliged to fight jihad in Afghanistan because there are foreign troops -- there is an Angriz (British) invasion," dishevelled Alahuddin told reporters.
"A Taliban commander, Saifullah, introduced us to a guide who escorted us to Barmal," he said. "Then he left and we joined a group already here and came to the ambush site."
It was only Alahuddin's second day in Afghanistan and it went horribly wrong.
His group of 32 Taliban lay in wait for an army convoy, launching a clumsy attack mainly with AK-47 machine guns.
The Afghan soldiers and their International Security Assistance Force (ISAF) counterparts retaliated. Two columns of support quickly arrived and surrounded the attackers as attack helicopters were called in.
After five hours of fighting, 24 Taliban and a soldier were dead. Some of the rebels not killed by the troops blew themselves up with their own grenades, soldiers said.
One of the dead had a Pakistani ID document on his chest when he was shown to reporters, while the others had other papers on them that the Afghan army said gave their nationalities.
Alahuddin said he was misled into believing that Afghanistan was overrun by foreign "infidels", especially the British forces hated since their 19th century wars in the region.
"We were sent to Afghanistan blindly. We call on our other friends in Pakistan and say, 'There is no jihad here, everybody is Muslim,'" he told AFP.
A few hours later, the three men were on the floor of a helicopter with their eyes taped shut being taken to Kabul for interrogation.
Political analyst Samina Ahmed, from the International Crisis Group, this week called the deal "irresponsible to say the least".
For "all practical purposes, now the Taliban are running the show," she told a meeting in Brussels.

Copyright AFP (Agence France-Presse), 2006