Since the beginning of Russia’s invasion, its attacks had periodically damaged energy infrastructure near the front lines. “That we were used to,” Dmytro Sakharuk, the executive director of DTEK, Ukraine’s largest private energy company, said. “But then they changed strategy.” Starting last fall, the Russian military began targeting coal-fuelled power plants, substations, and transformers across the whole of Ukraine. Russian officials wagered that by depriving Ukrainians of electricity—and, as a result, heat and water—during wintertime, they would sap the country’s resolve. “They wanted to initiate a long-term blackout and to freeze our big cities,” Volodymyr Kudrytskyi, the C.E.O. of Ukrenergo, told me. “The idea was to force us to negotiate not through emerging victorious on the battlefield but by terrorizing the population.”