Russia’s Secret War and the Plot to Kill a German CEO

On a clear night at the end of April 2024, arsonists slipped into a tidy residential neighborhood in Hermannsburg, a German village of about 8,000 people surrounded by flat farm fields, heathland nature reserves and military bases. Under the cover of darkness, they arrived at a large redbrick home, where they set fire to a clapboard garden house and a towering beech tree out front. They escaped undetected before the fire brigade arrived. Neighbors awoke the next morning to the smell of still-smoldering wood.

The home belonged to Armin Papperger, the chief executive officer of Rheinmetall AG, Germany’s ...