Mary Louise Kelly is NPR’s National Security correspondent. Her latest novel is “The Bullet.”

In the first pages of Ben Macintyre’s riveting new history, you learn that the idea for a revolutionary fighting force — a commando unit that became the prototype for special forces around the world — was conceived not in the heat of battle but from the acute boredom of a sickbed.

Specifically, the sickbed of one David Stirling. A less likely war hero would be difficult to imagine. In college, Stirling misbehaved on a lavish scale. “If he ever opened a book,” Macintyre writes, “the event was not recorded.” Nor did Stirling show promise as a young officer: “He lacked the most basic military discipline, could not march straight, and was so lazy his comrades had nicknamed him ‘the Giant Sloth.’ ”

But this sloth was also wily, charming and exceptionally clever, according to “Rogue Heroes.” “Stirling was one of those people who thrive in war, having failed at peace,” is how Macintyre succinctly puts it, and the story takes off from there.

Hooked yet? You will be.

"Rogue Heroes: The History of the SAS, Britain's Secret Special Forces Unit That Sabotaged the Nazis and Changed the Nature of War," by Ben Macintyre (Crown)

“Rogue Heroes” opens with Stirling at age 25 — skinny, grumpy and temporarily paralyzed from the waist down — moping in a hospital ward after a parachute jump gone badly wrong. Lying there, trying to wiggle his toes, Stirling cooks up a scheme to insert small groups of highly trained soldiers behind enemy lines, to carry out special operations against high-value targets. Put simply, Stirling was pondering ways that “a team of just five men could wreck an entire airfield in a matter of minutes.”

It’s worth remembering just how radical a concept that was, 75 years ago. Today, we’re so conditioned to the concept of asymmetric warfare as to find Stirling’s project unremarkable. But the generals to whom he reported understood war as two armies facing each other across a defined battlefield. An experiment that called for sneaking soldiers into the adversary’s camp, sabotaging equipment, then sneaking off again into the night? Scandalous. No, worse — it seemed unsporting.

“If [Stirling’s] idea was to have a chance, he would need to get the proposal directly into the hands of the most senior officers, before anyone lower in the hierarchy had a chance to kill it,” Macintyre tells us. Valuable advice for anyone navigating a bureaucracy, military or otherwise, and it worked for Stirling: On Nov. 16, 1941, the fledgling Special Air Service carried out its first mission. Code-named Operation Squatter, the plan was to parachute into the Libyan desert, infiltrate five airfields on foot, and blow up as many German and Italian planes as the team could find.

It was, Macintyre writes, “an unmitigated disaster.” Driving rain, gusting wind and whirling sand meant the men were jumping blind. Stirling hit the desert floor with such force he blacked out. Fifty-five men parachuted into the gale that night; just 21 returned. The rest were dead or injured, missing or captured.

Somehow Stirling turned this debacle into a learning experience. By December, the SAS had regrouped at a new forward base and was busy plotting assaults on the airfields of the Gulf of Sirte. How fared morale? Most of the men were “silently petrified.” But Macintyre notes that even in these early days of the SAS, a “peculiar camaraderie had already taken root, a strange esprit compounded in equal parts of ruthlessness, guile, competitiveness, and collective determination.”

Macintyre bases his account on unprecedented access to SAS regimental archives. Gathered by an SAS officer after World War II in 1946, they’ve been held in secrecy for 70 years. And what details Macintyre has gleaned from these dusty diaries and photographs! Even minor characters bristle with life. We meet a resourceful Egyptian butler who “possessed an uncanny talent for simultaneously mixing pink gins, obtaining ammunition and vehicle spare parts, and answering the telephone.” Two hundred pages later, we’re treated to an SAS officer invested with “an enormous moustache, a bluff sense of humour, an upper-class accent so fruity that the men barely understood his commands, and a habit of saying ‘what, what’ after every sentence, earning himself the nickname ‘Captain What What.’ ”

Macintyre even conjures up fresh material on such a familiar figure as Winston Churchill. Here is Britain’s celebrated wartime leader, making his entrance at a Cairo dinner party in 1942: “The prime minister was in ebullient form, wearing a bow tie and his velvet ‘siren suit’ — a military-style one-piece boiler-suit that would not become fashionable again for another seventy years.” (This is the rare Macintyre observation I feel compelled to question: Velvet one-piece boiler-suits became fashionable around 2012? Really? Am I the only one to have missed this development?)

This is a book about war, and some chapters make for uneasy reading. As the desert war in North Africa wound down, SAS forces moved north into Europe and eventually into Germany itself. On April 15, 1945, they became the first Allied soldiers to stumble on the Bergen-Belsen concentration camp. “The smell hit them first,” Macintyre writes. “The reek of pure evil, it grew steadily stronger as they advanced.” You know what they will find, but the details included here cause you to catch your breath anew at the horror that transpired there.

World War II ended in the European theater on May 8, 1945. The SAS was officially disbanded that October. But it soon sprang back to life, as the advantages of deploying a small, elite team on missions beyond the capability of conventional forces slowly dawned on commanders. “The SAS changed the face of warfare,” Macintyre concludes. You can track its legacy today in special forces around the world, including America’s Delta Force and Navy SEALs.

This is the spot in the book review where I’m supposed to find some point to quibble with, some omission, some historical inaccuracy, some flaw. Sorry to disappoint. The fact is Macintyre has produced yet another wonderful book. As Captain What What might have put it, this is a ripping good read.