After nearly a decade covering international conflicts, including the Russia-Ukraine war, for The Associated Press, Mstyslav Chernov makes his feature film debut with “20 Days in Mariupol.” The film draws on Chernov’s daily news dispatches and personal footage of his own country at war. It offers a vivid, harrowing account of civilians caught in the siege, as well as a window into what it’s like to report from a conflict zone, and the impact of such journalism around the globe. Now streaming on