An explosive device derailed a Russian freight train in a region bordering Ukraine for a second straight day Tuesday ahead of an expected counteroffensive by Kyiv. Russian territory and Crimea, annexed by Moscow in 2014, have been hit in recent days by a series of attacks. The last four days have seen two trains derailed by explosions, a suspected drone hitting an oil depot in Crimea that caused a huge blaze and power lines blown up near Saint Petersburg. The strikes come as Russia gears up to celebrate May 9, a holiday marking the Soviet victory over the Nazis that...