The English have always taken pride in civility, so it should come as no surprise that the government debated how to deal with Hitler as the Nazi war machine began lurching across Europe. The question: Should the war be conducted in the traditional British gentlemanly fashion?

A member of Parliament ridiculed the idea. “When you are fighting for your life against a ruthless opponent,” he told his colleagues, “you cannot be governed by the Queensbury rules.”

The rules concern few in the tight-knit group of Churchill’s Ministry of Ungentlemanly Warfare: The Mavericks Who Plotted Hitler’s Defeat (Picador, 368 pp., ***½ out of four stars), Giles Milton’s richly detailed narration of British government-sanctioned sabotage and other hit-and-run tactics against Germany.

The book is a fascinating account of England’s top-secret operatives who designed and deployed the chilling but effective weapons of clandestine warfare — mines, mortars, magnetic bombs — and others, agents who infiltrated behind enemy lines with orders to disrupt and kill. The guerrillas’ goal was to strike, vanish and leave no trace — leaving the enemy to decide if an act was sabotage, an accident or something else.

It’s a terribly bloody business and Milton, a best-selling British author, neither glorifies nor disparages it. He simply lets historical figures speak for themselves.

The secret group began forming in 1939. Winston Churchill championed it after becoming prime minister, convinced it was needed to defeat the Nazis. Some British officers and others in the War Office were horrified at this new type of warfare.

A general halts a guerrilla training session in which a sharpened trowel is demonstrated as a tool for cutting carotid arteries….