As Ukraine prepares for a major peace summit in June, President Volodymyr Zelensky sees an opportunity to free all Ukrainian prisoners from Russia before the end of the war. After the start of the full-scale invasion, Russia has seized thousands of Ukrainians, from soldiers to children, adding them to the hundreds of Ukrainian warfighters it was holding from earlier. Ukrainian authorities doesn’t disclose how many Russian prisoners of war (POWs) are currently in custody in Ukraine, nor how many POW detention centers there are in the country. “Some are skeptical, saying that (the all-for-all pr…