Who in Allied governments, the Vatican and the press knew what about the Holocaust and when? What could and should have been done to save Europe's Jews? Ever since World War II, those questions have been fiercely debated. Now, a United States government analysis suggests that while the evidence was incomplete, gruesome details from coded Nazi messages that Britain intercepted beginning in 1941 could have confirmed and exposed the scope of German genocide well before 1945, when Allied troops liberated the death camps and became witnesses to the horror. The analysis - titled "Eavesdropping on Hell" and written by Robert J. Hanyok, a historian with the National Security Agency's Center for Cryptologic History in Maryland - was quietly released last month. The analysis suggests that the Allies largely failed to understand the information they had, information that might not have given advance warning of the Holocaust, but could have prompted a military response that could have interrupted the deportations or mass exterminations or, at least a propaganda campaign against Nazi atrocities.