Contemporary conflict is as much about the manipulation of perceptions as it is about performance on the battlefield. Psychological operations have always been a component of warfare, but in today’s television, internet and social media-saturated environment, they play an outsized role. Military force is not obsolete, but perceptions are critical—and they can be shaped. Russia can hope to conquer Ukraine either by defeating its forces militarily or by outlasting the West’s resolve to continue supporting Ukraine’s defense — or possibly some combination of the two. The first requires success on the battlefield, which — despite Russian reinforcements, new commanders and...