TRIPOLI, Libya -- One brother joined the global jihad against the West under the nom de guerre Abu Yahya al-Libi. He rose to become Al Qaeda's brightest star and second in command, until an American drone strike killed him in Pakistan four months ago.
The other brother, Abdel Wahab Mohamed Qaid, was the first to become an Islamist militant but is now a moderate member of Libya's new Parliament.
As the United States weighs responses to the Islamist-led assault on its diplomatic mission in Benghazi that killed Ambassador J. Christopher Stevens, Mr. Qaid says the two brothers' diverging paths trace a timely lesson: a parable of the dangers of treating the many different strands of political Islam as a single radical threat.
Abu Yahya's support for Al Qaeda, Mr. Qaid said, began after his years as a prisoner at the Bagram Air Base in Afghanistan -- an account supported by Western analysts who have studied Abu Yahya's life.
Both brothers had previously shunned Osama Bin Laden and the cause of global jihad as irrelevant to their single-minded focus on ousting the Libyan leader Col. Muammar el-Qaddafi. But then, after the terrorist attacks of Sept. 11, 2001, and the United States-led invasion of Afghanistan, the Americans began rounding up any Islamist militants they could find, regardless of their specific ideology or agenda; Abu Yahya was captured in Pakistan and imprisoned without trial at Bagram.
When he finally escaped in 2005, picking a prison lock and evading his guards, Abu Yahya, originally known as Mohamed Hassan Qaid, was reborn as the leading theologian, propagandist and battlefield commander of an Islamic holy war against the West that left little room for local concerns like the struggle for Libyan democracy.
The older Mr. Qaid, speaking publicly for the first time, argued that Abu Yahya had been drawn into battle with the United States mainly because its military had treated him as an enemy. The vast majority of young Libyans, including many armed Islamists, now feel warmly toward America for its support against Colonel Qaddafi, Mr. Qaid said, and the impulse of United States officials and liberal Libyans to associate them all with Al Qaeda risks pushing them closer to the terrorist group.
"When they see they are lumped together with Al Qaeda, even those unsympathetic to it will become more sympathetic, and this would be the best gift you could ever give to Al Qaeda," Mr. Qaid said, charging that many Americans often treated all Islamists as shades of Al Qaeda.
Many other Libyan Islamist militants who had taken refuge from Colonel Qaddafi in Pakistan or Taliban-controlled Afghanistan have told similar stories, attesting that they were wrongly imprisoned and mistreated by the United States on suspicion of ties to Al Qaeda though their only fight was against the Libyan dictator. Last month, Human Rights Watch, a nonprofit advocacy group, documented more than 15 such cases of Libyan Islamists captured by the United States, including two who told the group that they had been subjected to a form of coercive interrogation known as waterboarding.
Unlike Abu Yahya, however, most of the captured Libyans never turned to Al Qaeda. Some are now playing prominent roles in their country's transition toward democracy. And, conversely, a few others enlisted in the Al Qaeda cause without American imprisonment or mistreatment.
Just what factors may have shaped the psychology of Abu Yahya or any other militant remains "highly speculative," said Brian Fishman, a researcher at the New America Foundation who previously worked at West Point studying terrorist movements. But "it is absolutely true that we failed to distinguish between Al Qaeda and a variety of Islamist militant groups that were operating in Afghanistan, and we should have distinguished between them because not all of them had accepted Al Qaeda's worldview," he said.
Mr. Qaid insisted that although he and his brother had both been militants, part of the Libyan Islamic Fighting Group determined to oust Colonel Qaddafi, they were never terrorists or enemies of the West.
Both brothers -- each the spit and image of the other, both known for their poetic gifts and theological knowledge -- were drawn into politics by the Libyan student movement of the mid-1980s. As a medical student at the University of Benghazi, Mr. Qaid said, he was appalled by the Qaddafi government's use of torture and public hangings to quell dissent. "I started to realize the scale of the oppression," Mr. Qaid said in lilting, classical Arabic, sitting in the cafe of the Rixos hotel here in a crisp white galabeya and prayer cap with a purple pillow scrunched in his lap.
By 1989, Mr. Qaid had fled to Tunisia, Pakistan, and elsewhere in international Islamist circles, and Abu Yahya, two years younger, followed in his footsteps two years later.
In 1995, Mr. Qaid crossed into Libya on a mission for the group when he was captured by Colonel Qaddafi's agents. At 28, he was sentenced to death but ultimately spent the next 16 years in the notorious Abu Salem prison in Tripoli. "I grew up in prison," he said.
As young men, Mr. Qaid said, he and his fellow Islamists had sometimes been overconfident in their "righteousness" and too ready to impose it on others, and they did not listen to the debates among older Muslim scholars.
"We used to think that removing oppression and imposing justice are the same thing, but justice requires dialogue," Mr. Qaid added. In prison, he said, he and many of his fellow Islamist inmates decided that just as they rejected Colonel Qaddafi's suppression of dissent, they should never try to impose their own views on others. "We want to derive our way of life from the teachings of our religion, without forcing anyone else to do it," he said. "These are the principles that never change."
He also adopted a less black-and-white approach to religion in public life. "In Islamic law, there is something called the science of balance," Mr. Qaid said. "You need to look at the context, see if something will do more harm than good before you practice it."
He said he considered secular Turkey the best model for an Islamist government in Libya, argued that tolerance and pluralism should be its watchwords and said it should rest on only those precepts of Islamic law that are "universal human values."
In time, the Qaddafi government began citing Mr. Qaid to show that some Islamist prisoners were reforming -- though it did not release him until the beginning of last year's uprising.
New inmates brought reports of Abu Yahya, who had settled among a circle of Islamist exiles in Pakistan and then Afghanistan. "Al Qaeda was everywhere" on the scene there, Mr. Qaid said, but the Libyan exiles rejected that path.
Western analysts confirm that the Libyan group was hostile to Al Qaeda. Jarrett Brachman, a counterterrorism consultant to the government who has studied Abu Yahya and the Libyan group, said that many of its members mistrusted Bin Laden and thought even less of his second in command, Ayman Zawahri. In Abu Yahya's poetry and other writings, "it was all Libya all the time," Mr. Brachman said.
But when Abu Yahya escaped, he found his Libyan comrades were almost all gone, detained by the United States or sent back to Colonel Qaddafi's jails. "Instead of finding the Libyans who could have absorbed his anger, Abu Yahya found Bin Laden," Mr. Qaid said.
Abu Yahya's escape made him a celebrity among anti-American militants, and he quickly rose to become second only to Mr. Zawahri after the death of Bin Laden. "His combination of scholarship, street cred and charisma made him a real heavyweight," said Mr. Brachman, and as Abu Yahya's stature grew, he increasingly attacked more moderate Islamists for betraying the cause of international jihad, indirectly taking aim at his older brother.
Mr. Qaid was freed, along with other political prisoners, the day after the Libyan uprising began in February 2011, in a bid to quell the revolt. He raced across the southern border, through Sudan and Egypt, and back into eastern Libya to join the fight.
In the interview, Mr. Qaid said he felt no bitterness over the drone strike that killed his brother in June. Mr. Qaid was running for Parliament at the time. "If there had been elections when we were students," he said, "maybe we would not have left school and the lives we had."
Suliman Ali Zway contributed reporting from Tripoli.
This article originally appeared in The New York Times.