Okean Elzy is one of the top bands in Ukraine. It has a kitschy, stadium rock style, and songs with patriotic themes that for decades have provided the soundtrack to anti-Russia protests. Tickets to its concerts are highly prized. But they suddenly became available after the first of three sold-out concerts in Kyiv, Ukraine’s capital, on Friday night. The reason? Draft officers and the police had waited outside the concert hall, looking for men trying to dodge military service in the country’s war with Russia. They asked men to see their draft papers and detained those who had not registered....