Very underrated: 1948's The Search. It's about a boy who survived the Holocaust but got separated from his mom. She also survived and both are looking for each other. The boy gets help from a young GI played by Montgomery Clift in one of his first roles, he got an Oscar nomination for it (the film won two Oscars, one for "Best Story" and one special award for the best child performance). A lot of scenes were filmed on location in the bombed out ruins of Germany and it doesn't shy away from depicting the PTSD of all those displaced children, but it's ultimately a hopeful film with some moments of levity.