Some 170 miles southwest of the celebrated landing beaches in Normandy, the remains of a D-Day site few visit peek out from behind trees in rural Brittany.

Overgrown with moss and ivy, the stone farm buildings were the former headquarters of the Saint-Marcel Maquis — thousands of local French resistance fighters who had gathered in response to coded Allied calls over BBC radio to prepare for an invasion. Among them were French army commandos parachuted in to block the Nazis from sending reinforcements to the beaches.

But before the operation could be put into full swing, the camp was discovered by the Nazis and destroyed. Dozens of fighters were hunted down and killed. In retribution, most buildings in the surrounding area were burned and hundreds of locals were executed.

It’s a wound of tragic heroism that few in France know about, let alone commemorate.

President Emmanuel Macron of France hopes to change that on Wednesday when he presides over a ceremony in Plumelec, the nearby village where French commandos landed early in the morning of D-Day as the first Allied planes and gliders were arriving in Normandy. One of the members of that elite French unit, Émile Bouétard, was shot dead by soldiers with the German army. He is considered among the first Allied casualties of D-Day.

The president’s visit will be the latest in a year of events planned to celebrate the country’s release from the Nazis’ grip 80 years ago. Unlike many of his predecessors, Mr. Macron has chosen to memorialize not only the valiant and brave, but also the shameful and forgotten — including a site where French resistance fighters were killed by French militia members who were working with the Nazi regime.