Complex sentence: Estimates range from 30,000 to 55,000 killed between spring and autumn 1945, mostly prisoners of war repatriated by the British military authorities from Austria, where they had fled, died in these post-war summary executions.
Split into simpler sentences: Estimates range from 30,000 to 55,000 killed between spring and autumn 1945. mostly prisoners of war repatriated by the British military authorities from Austria, where they had fled, died in these post-war summary executions.