Russian mercenaries are the all-too-real bogeymen of the war in Ukraine. Most belong to the company known colloquially as Wagner, a quasi-corporate paramilitary group connected to the Kremlin that serves as a violent tool of Putin’s foreign policy around the world. Depending on the reports you believe, Wagner mercenaries were responsible for the execution of civilians in Bucha, have deployed tens of thousands of infantry to support the eastern offensive, or have already lost 3,000 fighters in combat. Deliberate disinformation surrounds their operations, and initial reports are just that, but Wagner mercenaries often leave evidence behind, and so there are...