As he sits in Geneva, Michel Dreifuss does not feel all that far away from the Hamas attack on Israel on Oct. 7 and Israel’s subsequent bombardment of Gaza. The ripples are rolling through Europe and upending assumptions both global and intimate — including those about his personal safety as a Jew. “Yesterday I bought a tear-gas spray canister at a military-equipment surplus store,” the 64-year-old retired tech sector worker said recently at a rally to mark a month since the Hamas killings. The choice, he says, is a “precaution,” driven by a surge of antisemitism in Europe. Last month’s...