When Daniel Rouxel was a small boy growing up in the Breton village of Megrit in the early 1950s, he remembers the mayor making him stand up in front of the parishioners outside church one Sunday.
"Which one of you knows the difference between a swallow and a Boche?" the mayor asked.
"I'll tell you. When the swallow makes its babies here in France, it takes them with it when it leaves. But the Boche - he leaves his behind."
The author hopes to encourage people to trace their fathers
Rouxel was, not surprisingly, mortified. He was the baby the Boche had left behind.
"After that, I wept and wept," he says today. "I was so ashamed that I ran and hid under a bridge for the whole night. I even thought of doing away with myself."
Rouxel's account appears in a book just published in France - coincidentally or not, just before the 60th anniversary of the liberation. It finally addresses one of the country's last remaining wartime taboos.
"Enfants maudits" - or "Accursed Children" - collects in print, for the first time, memories of the tens of thousands of so-called "Bastards of the Boche", the illegitimate offspring of liaisons between French women and occupying German troops.
According to research cited by author Jean-Paul Picaper, a staggering 200,000 were born between 1941 and 1945 - a long-neglected generation of people now entering their 60s, who are at last able to speak out about the shame and trauma they went through.
Like Daniel Rouxel, most of the children were born as a result of affairs between lonely, bored young women and troops billeted nearby. Rape was not a factor.
However, Nazi rules prohibited marriage with French natives - unlike with Norwegians or Dutch who were deemed to be "Aryan". So the liaisons were secret and often ended abruptly when they were discovered.
After the war, the mothers went through purgatory as France was swept with a tide of anti-German hostility and collaboration amnesia set in. Many were paraded through the streets with heads shaved, and some sent to jail for offences against "national dignity".
But the book shows that for the Franco-German children of the war too, the psychological effects of their in-built sense of humiliation and rejection were to be profound and long-lasting.
Michelle Colin for example, who was handed over to an orphanage when she was a few weeks old, recalls being made to write out over and again in her jotter the words, "I am the daughter of a Boche."
Jeanine, who was born in 1941 near Rouen, was literally struck dumb for several months when she learned of her German father at the age of 13.
"In the street it was sheer terror," she says. "To be the child of the occupier was traumatic. In those days people in the village spoke of the cruelties committed by the Germans. Everyone expressed deep hatred towards them. I was afraid of being the daughter of a 'murderer'."
Daniel Rouxel says that his blonde hair and blue eyes were a constant affront to the grandmother who brought him up. She beat him and locked him in the hen coop.
Sixty years on, none of these stories has been told before and there is no network or forum to allow the war-children to share their experiences.
Picaper ran into serious difficulties tracking them down, but his breakthrough came when he contacted the archives of the German Wehrmacht in Berlin.
There he found that officials were coping with a steady stream of letters from France asking for help in finding long-lost fathers. He was able to put out feelers, though most of those who agreed to talk to him did so anonymously.
Picaper says the aim of the book is to encourage more of the 200,000 to emerge from the shadows, and in each copy is included a form which can be sent to the Wehrmacht archives.
"They are among us, a little more blonde perhaps but not necessarily so," he writes. "They have kept their secret since childhood... Accustomed to the clandestine, they rarely speak openly of their past and only open their heart to a few friends or their spouse.
"Today, at the age of retirement, they feel more and more inclined to speak out. What they would like to understand most of all is why... they still feel responsible for a sin they never committed."