Silver Sword by Ian Serraillier
9780099572855 Vintage Classics
"If you meet Ruth or Edek or Bronia, you must tell them I'm going to Switzerland to find their mother. Tell them to follow as soon as they can" Having lost their parents in the chaos of war, Ruth, Edek and Bronia are left alone to fend for themselves and hide from the Nazis amid the rubble and ruins of their city. They meet a ragged orphan boy, Jan, who treasures a paperknife - a silver sword - which was entrusted to him by an escaped prisoner of war.
The three children realise that the escapee was their father, the silver sword a message that he is alive and searching for them. Together with Jan they begin a dangerous journey across the battlefields of Europe to find their parents.