U-Boats

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…than if they sailed independently. But by 1939 there were not enough escorts, and ships with speeds greater than 5 knots were encouraged to sail independently. The German U-boats concentrated on ships that were not in convoy. In the end the U-boats were defeated. The British started dropping depth charges, and attacked by air. That with the use of convoys helped Britain protect itself from the German U-boats. World Book Encyclopedia, Volume 18, 1988 U-boat, under the Swastika, Showell, 1973