Difficult to locate, U-boats posed a significant threat to Allied shipping in the Atlantic. However, Allied leaders could pinpoint U-boats by successfully intercepting Axis radio transmissions between ships at sea and shore-based headquarters. Using radio bearings, Anglo-American trackers deprived U-boats of the tactical advantages of submarine stealth and surprise, rerouting Allied shipping out of harm's way. According to German records, approximately 870 U-boats actively participated in the Battle of the Atlantic on war patrols. Of that number, fewer than 330 U-boats actually logged successful attacks against Allied vessels by 1945. Such figures illustrate the significance of Anglo-American intelligence in limiting the U-boat threat to Allied shipping.