The case of an alleged Russian mole inside Germany’s intelligence service has raised alarms in Berlin, where Russia has long spied aggressively and may have assassinated a foe.

BND Headquarters in Berlin

A widening investigation into alleged Russian spying inside Germany’s state intelligence service, the BND, has set off alarm bells in Western capitals and prompted calls for a major overhaul of the agency to shore up its defenses against Russian espionage.

Coming at a crucial moment in the war in Ukraine when the United States a…