World leaders using diplomacy and dire warnings to stop Russia from invading Ukraine
As Britain's Prime Minister Boris Johnson says Russia is preparing to start the biggest war in Europe "since 1945," Ukraine's President Volodymyr Zelensky is calling for a ceasefire in the east of Ukraine, where Russian troops are stationed just across the border. But as CBS News correspondent Charlie D'Agata reports, Russia is showing no signs of stepping back from the brink of war.