PARIS — They are among France’s darkest days: Police dragged over 13,000 Jews from their homes, confined them in a Paris cycling stadium with little food or water, and then deported them to their deaths in the concentration camp at Auschwitz. But even in France, one of the most brazen collaborations between authorities and the Nazis during World War II is unknown to many in the younger generation.

Police are hoping to change that, opening up their archives on France’s biggest single deportation of French Jews for the first time to the public on Thursday.

The often chilling records are being exhibited in the Paris Jewish district’s city hall to coincide with the 70th anniversary of the two-day “Vel d’Hiv” roundup, named for the Velodrome d’Hiver, or Winter Velodrome. Many thousands were rounded up on July 16 and 17, 1942, then holed up in miserable conditions in the stadium, just a stone’s throw from the Eiffel Tower, before being bused to the French camp at Drancy and then taken by train to Auschwitz....