You might want to take a look at the work of Scott Atran (from the Univ of Michigan; his other job, Directeur de Recherche, Anthropologie, Centre National de la Recherche Scientifique, Paris). He has a huge literature. Here are some samples, expressing the "band of brothers" approach:

Talking to the Enemy: Faith, Brotherhood, and the (Un)Making of Terrorists (2010) (on my book shelf):

Atran interviews and investigates Al Qaeda associates and acolytes, including Jemaah Islamiyah, Lashkar-e-Tayibah, and the Madrid train bombers, as well as other non-Qaeda groups, such as Hamas and the Taliban, and their sponsoring communities, from the jungles of Southeast Asia and the political wastelands of the Middle East to New York, London, and Madrid. His conclusions are startling, important, and sure to be controversial.

Terrorists, he reminds us, are social beings, influenced by social connections and values familiar to us all, as members of school clubs, sports teams, or community organizations. When notions of the homeland, a family of friends, and a band of brothers are combined with the zeal of belief, amazing things—both good and bad—are possible: the passage of civil rights legislation, the U.S. Olympic hockey team's victory in 1980, the destruction of 9/11 and the attacks on the London Underground in July 2005.
PATHWAYS TO AND FROM VIOLENT EXTREMISM: THE CASE FOR SCIENCE-BASED FIELD RESEARCH - Statement Before the Senate Armed Services Subcommittee on Emerging Threats & Capabilities (2010):

Summary: De-radicalization, like Radicalization, is Better from Bottom Up than Top Down

When you look at young people like the ones who grew up to blow up trains in Madrid in 2004, carried out the slaughter on the London underground in 2005, hoped to blast airliners out of the sky en route to the United States in 2006 and 2009, and journeyed far to die killing infidels in Iraq, Afghanistan, Pakistan, Yemen or Somalia; when you look at whom they idolize, how they organize, what bonds them and what drives them; then you see that what inspires the most lethal terrorists in the world today is not so much the Koran or religious teachings as a thrilling cause and call to action that promises glory and esteem in the eyes of friends, and through friends, eternal respect and remembrance in the wider world that they will never live to enjoy.

Our data show that most young people who join the jihad had a moderate and mostly secular education to begin with, rather than a radical religious one. And where in modern society do you find young people who hang on the words of older educators and "moderates"? Youth generally favors actions, not words, and challenge, not calm. That's a big reason so many who are bored, underemployed, overqualified, and underwhelmed by hopes for the future turn on to jihad with their friends. Jihad is an egalitarian, equal-opportunity employer (at least for boys, but girls are web-surfing into the act): fraternal, fast-breaking, thrilling, glorious, and cool. Anyone is welcome to try his hand at slicing off the head of Goliath with a paper cutter.
“Band of Brothers”: Civil Society and the Making of a Terrorist (2008):

Soccer, paintball, camping, hiking, rafting, body building, martial arts training and other forms of physically stimulating and intimate group action create a bunch of buddies, which becomes a “band of brothers” in a simple heroic cause. It’s usually enough that a few of these buddies identify with a cause, and its heroic path to glory and esteem in the eyes of peers, for the rest to follow even unto death. Humans need to socially organize, to lead and be led; however, notions of “charismatic leaders” and Svengali-like “recruiters” who “brainwash” unwitting minds into joining well-structured organizations with command and control is exaggerated. Viewed from the field, notions of “cells” and “recruitment”—and to a degree even “leadership”—may reflect more the psychology and organization of those analyzing terrorist groups than terrorist groups themselves (see Marc Sageman’s Leaderless Jihad, University of Pennsylvania Press, 2008).

Takfiris (from takfir, “excommunication”) are rejectionists who disdain other forms of Islam, including wahabism (an evangelical creed preaching Calvinist-like obedience to the state) and most fundamentalist, or salafi, creeds (which oppose fighting between co-religionists as sowing discord, or fitna, in the Muslim community). They tend to go to violence in small groups consisting mostly of friends and some kin (although friends tend to become kin as they marry one another's sisters and cousins—there are dozens of such marriages among militant members of Southeast Asia's Jemaah Islamiyah). These groups arise within specific “scenes”: neighborhoods, schools, workplaces, and common leisure.
Regards

Mike