Russia announced the arrest of Evan Gershkovich, a correspondent at The Wall Street Journal. He is believed to be the first American reporter to be held as an accused spy in Russia since the collapse of the Soviet Union. The arrest was a stunningly provocative move, aimed at one of the best-known Western journalists still working inside Russia and his employer, a pillar of the American news media. With the arrest, President Vladimir Putin signaled to the world that he was doubling down on Russia’s wartime isolation. Gershkovich, like other Western journalists, had the Kremlin’s formal approval to work there. But Russia’s options for retaliation have grown increasingly limited, Europe has largely weaned itself off its dependence on Russian energy imports, and major Western companies have largely cut ties with Russia. Western journalists have thus become one of the few remaining potential pressure points, as a possible spring offensive looms. Gershkovich, 31, grew up in Princeton, N....