Ukraine's President Volodymyr Zelenskyy is gambling that his surprise attack into Russia can convince Vladimir Putin to negotiate an end to the 2½-year-old war which has produced an estimated one million casualties. But Putin's forces continue to rely on the sheer weight of numbers to grind Ukraine down, and Zelenskyy must depend on America's deeply divided politics for the aid which he needs to stave off Russian assaults on his front lines and air attacks against his cities. CBS News national security correspondent David Martin talks with former Joint Chiefs Chairman Mark Miley about the stakes.

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