As one drives around the back roads of rural south-west France, where I live for part of the year, it’s quite common to come across a small, well-maintained obelisk on the verge. These modest memorials – usually inscribed with a few names – are testimony to some forgotten firefight between German soldiers and members of the French Resistance (“fusillés par les Allemands”) that took place during the dark days of 1940-44. The victims of these brutal encounters were soldiers on the front line, as it were; in harm’s way and, if not shot in some ambush, then liable to be arrested, tortured, sent to concentration camps or executed.

But, as Harry Rée’s striking memoir makes clear, for all the Resistance’s derring-do it was the secret army of “passive supporters” that allowed the French Resistance, and its British allies, to function at all. These unnamed, forgotten people provided safe houses and hiding places, stored munitions, passed on messages and supplied food, water and shelter when required. In effect they did nothing overtly heroic but their quiet participation in the struggle against the occupation often meant that their lives were as much on the line as the most daring guerrila in the rural Resistance, known as the Maquis. Harry Rée takes pains to make this point again and again in this short and remarkable history of his own years as an officer in the Special Operations Executive and his experiences as an SOE agent in occupied France. The SOE was variously known as “Churchill’s Secret Army” or the “Ministry for Ungentlemanly Warfare”. Its remit was to conduct espionage, sabotage and reconnaissance in occupied Europe. At its height, the organisation employed some 13,000 people, of whom more than 3,000 were women.

Harry Rée was a grammar school teacher when war broke out in 1939 – hence this book’s title. He joined up but after a few months in the artillery realised that the orthodox British army was not for him. The feeling was mutual. Rée argued that if he was going to be killed in the line of duty he would prefer that it was as a result of his own mistake rather than a consequence of an order “from some stupid colonel or general back at base”. So he joined the SOE and underwent the usual rigorous training in the dark arts of sabotage, communications and the running of a cadre of local résistants.

He was parachuted into France in 1943. He was 29 years old, married and his wife was heavily pregnant. Harry’s area of operations – codenamed “Stockbroker”– was in eastern France, in the Jura region between Dijon and Besancon. This book, edited by his son Jonathan Rée, is an account of the adventures he had in his months of covert activity. And “adventures” is the right word: Rée himself spoke of his time in France as a form of permanent “summer holiday”, and from time to time the account does read as if it were a tally of japes and scrapes and taunting the beastly Boche.

It seems remarkable now that not only was Rée married and soon to be a father but that his French was not particularly fluent (he was often introduced as a “cousin” from Alsace to explain his curious accent). His natural eccentricity and high spirits made his presence more perilous that it needed to be. Take, for example, his description of turning up one day at the railway station in Tarbes to catch a train to Clermont-Ferrand: “I reached the station an hour early, so I went and got my hair cut. I could hardly understand a word but said ‘oui’ to everything and came out with a reasonable haircut.”

But despite this air of ditsy English sang-froid it is clear that Rée was in fact a singularly successful SOE operative. Among other acts of sabotage and reinforcement of local resistance units, he was responsible for the extrajudicial assassination of a Maquis double agent, but his greatest success was the organisation of the near-continual sabotage of the Peugeot plant at Sochaux, which was then involved in making spare parts for German tanks. He persuaded the RAF not to bomb the factory as his group of saboteurs on the inside was far more efficient than any payload of bombs.

A Schoolmaster’s War is an unusual collage of a book – hence the editorial presence demanded of Jonathan Rée. There is a first-person memoir supplied by Harry Rée himself, written shortly after he had left the Jura, and then a compilation of a series of postwar talks Rée gave (with some reluctance) about his experiences. As a bonus, there are children’s stories in which he had recounted thinly disguised versions of his exploits and then a whole series of letters written to him from his French contacts after the Liberation.

It’s clear that “Monsieur Henri”, as he was known to his French colleagues, was both much loved and revered. It’s only through these oblique testimonials that we gain a sense of the young man that he was and the loyalty he inspired. The frontispiece portrait of the young Rée makes him look like a handsome adolescent. It’s almost impossible to imagine such a person parachuting by night into occupied France and setting up his SOE networks. But that is part of the myth of special operations – a myth that Harry Rée was more than happy to demythologise.

The reality was altogether more torrid and, in human terms, more costly. Jonathan Rée provides a handy biographical overview of his father’s life at the book’s conclusion, along with a list of dramatis personae and a useful bibliography. Paradoxically and gratifyingly, the parts prove to be greater than the whole. A Schoolmaster’s War succeeds in its aleatory patchwork, ending up as a singularly sincere and moving account of one man’s war and how his experiences shaped his world-view irrevocably.

Rée’s climacteric occurred at the end of 1943 when, making a visit to a supposed safe house, he instead found himself confronted by a German member of the feld-gendarmerie (military police), who intended to arrest him. What followed was a vicious hand-to-hand fight during which Rée broke a bottle of wine over the feldgendarme’s head and the German emptied the magazine of his automatic pistol into Rée’s torso. Rée felt nothing, assuming the magazine was full of blanks, and the fight continued.

I lunged at him and brought him down. I remembered King Lear and tried to get one of his eyeballs out by pressing with my thumb. It didn’t work, so I tried biting his nose, and then put a finger in his mouth and tried to rip his cheek. That must have hurt a lot but he managed to push me off and stand up. I lunged and we started boxing again… I landed two more punches full in the face, smashing his head against the wall. He turned away and said, “Sortez, sortez”… get out.

Rée took him at his word and did. Only later did he discover that two bullets had passed through him – missing vital organs – and four others had grazed him. Amazingly, so critically wounded, he managed to cross fields and ford streams and arrive at another safe house. He was patched up and smuggled into Switzerland, where he continued to run his network from his sickbed, until, summoned back home, he crossed France to Spain and made it back to Britain.

The Bulldog Drummond spirit didn’t last. Rée’s postwar writings offer a darker, more considered tone. He reflects on the sacrifices that the ordinary people made, the passive supporters, and that, while their efforts allowed his network to flourish, they also suffered and lost members of their families – daughters, sons and husbands and wives. After the war, visiting the relatives of one of the families, the Barbiers, that had sheltered him (both Monsieur and Madame Barbier had died in concentration camps) he reflected:

I owed my survival to people like the Barbiers, as well as to Mme Fouillette, and to so many people like them. When people over here [England] think about the Resistance, such heroines and heroes can all too often be left out. They don’t deserve to be. They all deserve medals for bravery.

This is the theme that Harry Rée repeats again and again, almost as dogma, and, one senses, in this passionate and moving memoir, that it was the key fact that he retained from his wartime exploits. The tone becomes muted and saddened, the wisdom gained at an awful price: “Though wars can still bring adventures which stir the heart, their true nature is of innumerable personal tragedies, of grief, waste and sacrifice, wholly evil and not redeemed by glory.”

William Boyd is the author of “Trio” (Viking), to be published in October

A Schoolmaster’s War: Harry Rée, British Agent in the French Resistance

Edited by Jonathan Rée

Yale University Press, 192pp, £14.99