And late last year, in perhaps the most disturbing case of all, a German intelligence officer was unmasked as a mole passing surveillance of the war in Ukraine to Moscow.

Germany’s foreign ministry has been tight-lipped about the latest expulsions — even refusing to call them expulsions. But it acknowledged the diplomats’ departure was linked to “reducing the Russian intelligence presence in Germany.”

Expulsions were long a common German response to Russian operations — including the first parliamentary hack, in 2015, and the invasion of Ukraine, when 40 diplomats were sent back to Moscow. But security experts see the current move as part of a broader effort to bolster counterintelligence and chip away discreetly at what they long warned was an extremely high spy count at the embassy.

Still, analysts like Stefan Meister, of the German Council on Foreign Relations, said years of neglecting counterintelligence would take a long time to repair. When he worked with German spy agencies in 2000, he recalled, they did not have a single Russian speaker on staff. In contrast, he said, Russia’s president, Vladimir V. Putin, had long made Germany, Europe’s largest economy, a top target for espionage.