Aaron Cohen, a Canadian Jewish boy from Montreal, made aliyah in 1997 by way of Beverly Hills, Calif. He was not your garden variety immigrant.

Obsessed by the exploits of the Israeli army, he joined one of its special forces, Sayeret Duvdevan, whose stock-in-trade is counter-terrorism. As a member of this elite squadron, Cohen, often masquerading as an Arab but once disguised as an American journalist, hunted down Palestinian terrorists in the West Bank. In general, his targets were planners and fundraisers rather than suicide bombers.

And herein lies a crackling tale of high adventure. In Brotherhood of Warriors (HarperCollins), Cohen and his co-author, Douglas Century, trace a young man’s  remarkable trajectory from Canadian civilian to Israeli commando. It is quite a performance.

Cohen, born in Montreal in 1976, was the scion of an old established Jewish family. When he was small, his parents separated, and he spent the next number of years bouncing between homes in Montreal and Miami. When his self-absorbed mother – a film and television writer and producer – married Abby Mann, the screenwriter who won the 1961 Academy Award for Judgment at Nuremberg, Cohen moved to Los Angeles.

Mann was indifferent to Cohen, treating him “like a piece of furniture.” The boy rebelled and had problems with authority. In the ninth grade, he was enrolled at a military academy in the Niagara Peninsula in Ontario. The school’s headmaster, a Canadian army colonel who had been involved in Middle East peacekeeping in the 1970s, admired the Israelis. His admiration rubbed off on Cohen. As the young man studied Hebrew, he dreamed of settling in Israel, becoming a citizen and enlisting in an all-volunteer special forces squadron.

He arrived in the Promised Land with a duffel bag of clothes, a few Hebrew books and a cellphone, eager to fulfil his Zionist dream. He worked in a kibbutz fish pond until it was time to try out for the special forces. The gibushim, or tryouts, tested him to his physical and mental limits. He sprained an ankle, but persevered. “There was no way I was going to quit,” he writes with typical bravado.

Cohen did not have the right stuff for Sayeret Matkal, the legendary special force he aspired to join, but was recruited by Sayeret Duvdevan, which was formed during the first Palestinian uprising.

He describes the training regimen as  brutal. “In the United States and European democracies, our instructors’ behaviour and institutional hazing would be considered sadistic, borderline criminal, an open invitation to class-action lawsuits.” To survive, he adds, “we had to become emotionless, automatons, pure fighting machines.”

Having survived the first phase, he was transferred to a top-secret Duvdevan base in the West Bank that resembled a Palestinian village. There he morphed into a commando. He learned how to use the short-barrelled M-16 gun and fire accurately from the window of a moving vehicle. He learned krav maga, a “full-contact fighting” martial art. He carried 70 pounds of gear on his back on difficult forced marches. He picked up the rudiments of conversational Arabic, how to look, talk and act like a Palestinian and how to disguise himself as one.

The gruelling training hardened Cohen, altering him forever. “It [hardwired] a brand of aggression that [became] impossible to turn off,” he writes. Yet he revelled in his new identity. “Clearly, I was getting something vital out of the Israeli army that I hadn’t gotten from my dysfunctional show business family back in L.A. The bottom line for me was this: I’d never been happier. I had earned a place among the world’s best fighters, and I had been granted tremendous responsibilities to do an important job. I loved being accepted into Duvdevan more than anything I could ever have imagined.”

On his first mission as an undercover operative, his unit was dispatched to Ramallah to arrest a Hamas terrorist. Cohen’s job, in a supporting role, was to secure the perimeter while an entry team flushed out the suspect from a house. To his credit, he admits that he was frightened, nervous and skittish. The operation unfolded perfectly, without a shot being fired.

Whenever possible, he says, violence was avoided: “Terrorist leaders and masterminds are no good to us as corpses. We want the information they can provide.”

Yet fisticuffs occurred. Once, posing as a reporter, he “interviewed” a senior Hamas official at a cafe. As they talked, Cohen formed a “strong, genuine connection” with him. But when Cohen received a signal to incapacitate him, he reverted to form, jumping across the table and punching him in the face as hard as he could, with the result that Cohen needed 15 stitches to close his knuckle wound. On another occasion, Cohen was attacked with a knife by a middle-aged Palestinian woman. In self-defence, he struck her with his rifle butt, splitting open her chin.

In the only case of deadly force he mentions, Cohen opened fire on a Palestinian teenager, a Hamas courier, who had ambushed him. He hit him between the eyes, killing the Palestinian youth. Cohen was devastated: “I didn’t sign up to kill kids.”

He describes still more operations, including a complex one tasked with the mission of arresting a Hamas official who had organized a suicide bombing in Tel Aviv in 1996. On this operation, which went off without a hitch, Cohen posed as a sweet corn vendor as his companions stormed a wedding in progress.

At this point, he was burned out. “It takes a special type of personality – an intense level of commitment – to function long-term as a professional warrior,” he says.

Having decided to quit after three years of service, Cohen booked a flight back to the United States in the summer of 2000. He does not really explain why he left Israel after resigning from the army. In Los Angeles, he was depressed, subject to radical mood swings. Having regained his bearings following a six-month stint as a drill instructor at his old military academy in Canada, he returned to Los Angeles and began working for a company specializing in “celebrity security.”

For the next year and a half, he was in charge of a detail that protected actor Brad Pitt’s mansion in Hollywood. Cohen is virtually mum  about this chapter in his life, but it must have been incredibly boring.

In short order, he established his own company, IMS Security, staffed exclusively by ex-members of Israel’s special forces. “Our reputation spread fast, and we started signing up several big-ticket accounts, doing celebrity protection for A-list stars such as Jackie Chan and Arnold Schwarzenegger.”

IMS also guarded private Jewish schools in southern California. In the main, Cohen’s focus was counter-terrorism: firearms training, SWAT-like takedowns and hostage crisis management.

Since the terrorist events of Sept. 11, 2001, Cohen’s expertise has been in even higher demand. “I knew that the United States was far too vulnerable to Islamic terrorist attacks and I hoped I could do my part to sound the alarm,” he observes.

By any yardstick, he has succeeded, both as a security consultant and in this engrossing book.