In 1950, Robert Doisneau photographed a kiss you’ve surely seen. The man and woman seem to have been stopped by ardor amid the midday rush, in front of the Hôtel de Ville, Paris. Though staged, it became, nearly immediately, one of the most iconic images of the 20th century.

Surely unknown to Mr. Doisneau, nine years earlier, there was another kiss captured on film in Paris that was much more spontaneous, just as passionate — far more desperate — between two Jews about to be separated by the Vichy police. This kiss, found on a contact sheet of Nazi propaganda images in a Reims flea market six years ago, is now at the heart of a new exhibition of 98 Nazi propaganda photos at the Shoah Memorial in Paris curated by Lior Lalieu and me. This kiss, perhaps destined to become just as iconic, reveals a very different midcentury Parisian moment.

The photos provide a detailed visual account — almost minute by minute — of the very first, and little-known, roundup of Jews in France on May 14, 1941. That day, some 3,700 foreign-born Jews obeyed a summons by Paris police with a notice, printed on light green paper (it became known as the “green ticket roundup”), for what they believed would merely be a check of their immigration and identity papers. The operation was organized by a man named Theodor Dannecker, the envoy of Adolf Eichmann in Paris. A photographer with the Nazi propaganda unit in the city was on hand to observe.

What gives these newly discovered photographs their singular power is not only what they show but the fact that they survived at all. They remind us that the past is never entirely buried, and that images can unexpectedly return to challenge the void of memory and representation. They function today not as propaganda, the purpose for which they were originally produced, but as fragments of truth — painful, incomplete and indispensable — that allow us to better understand the way the roundup was organized and conducted and also to get a glimpse of the victims’ shock, fear and pain.

There are only a few hundred photographs of roundups or murders of Jews from the 1930s and 1940s, a disparity of mass proportion considering the extent of the genocide. Some were taken by victims as acts of resistance, some by bystanders, and others, like this collection, were by an authorized photographer for the Nazi propaganda machine. From time to time, grandchildren of Nazi perpetrators find these images in attics and boxes when the older generation dies.

This particular group of photographs was meant to document a Nazi success story. They begin with the trap: Jewish men and their spouses were summoned to over 60 locations in Paris — police offices, various administrations and a sports facility in the 11th Arrondissement. Women, we know from eyewitness testimony, were asked to return home to gather items; a list was provided. When they returned, as the images we now have on hand show, they were barred from reuniting with their male relatives. The doors were closed and guarded by French policemen. We can see the women’s pain, their bewilderment, many with bundles in their arms. We see couples as they part.