When Russian forces bombarded the Ukrainian city of Mariupol nearly two years ago, journalist Mstyslav Chernov and his colleagues with the Associated Press stayed in the besieged city to document the horrendous humanitarian crisis. The footage they managed to transmit to the world opened eyes to the horrors of the Russian attack, and is now the basis of his Oscar-nominated documentary, "20 Days in Mariupol." CBS News national security correspondent David Martin talks with Chernov about the suffering he witnessed. He also talks with Ukrainian soldiers wounded during last year's counter-offensive; and with Senator Angus King, who says ending American aid for Ukraine's war will be "the greatest geopolitical mistake this country has made in generations." Air Date: Feb 18, 2024