Zelenskyy is gambling that his surprise attack into Russia can convince Putin to negotiate an end to the 2½-year-old war which has produced an estimated one million casualties. But Putin continues to rely on the sheer weight of numbers to grind Ukraine down.

Ukraine's foreign minister said on Saturday that Russia is planning strikes on Ukrainian nuclear facilities before the winter, and urged the U.N.'s nuclear watchdog and Ukraine's allies to establish permanent monitoring missions at the country's nuclear plants.