Twelve months before the U.S. presidential election, U.S. Air Force Lt. Col. Jarred Prier got a taste of Russia’s covert efforts in American political affairs without recognizing the flavor.It was November 11, 2015. Prier was in Washington browsing Twitter for news about his alma mater, the University of Missouri, where racial protesters had just succeeded in ousting the university system’s president.#PrayForMizzou was trending. Backlash against the protesters had escalated fears of violence on campus. Intrigued, Prier began pouring over tweets supportive of Mizzou protesters. Activists on the ground were sharing minute-by-minute updates of campus, where encamped protesters had claimed the...