Secret torpedo with acoustic sensor tracking nose cone. This U-534 submarine was sunk after the German Navy had surrendered. However, this submarine, in a pack of three, failed to display the surrender flag, so was attacked by the Allied forces. Although nominally a training and weather-information collecting vessel, it happened to be carrying one of just two dozen latest-technology acoustic 'homing' torpedos. Question: was the sub attempting to deliver the high tech torpedo weapon to the Japanese, who had not yet surrendered? Nearly all of the crew were captured, but the cap[tain later committed suicide. The mystery continues unanswered.