capture of U-505. In 2006, screenwriter David Ayer admitted that U-571 had distorted history, and said that he would not do it again. He told BBC Radio 4's The Film Programme that he "did not feel good" about suggesting that Americans, rather than the British, had captured the naval Enigma cipher: "It was a distortion...a mercenary decision...to create this parallel history in order to drive the film for an American audience. Both my grandparents were officers in the Second World War, and I would be personally offended if somebody distorted their achievements." Technical inaccuracies The Kriegsmarine destroyers rarely ventured out into the open Atlantic Ocean, but usually stayed in European coastal waters. During the destroyer's depth charge attack more than eighty depth charges are detonated in the film, despite the fact that they rarely carried more than thirty. The German resupply U-boat would most likely not have been sunk by U-571. This would have been difficult for a German U-boat to achieve, as German sonar was not as advanced as British during the war. The only instance of a submerged submarine sinking another submerged vessel was in February 1945 when sank with torpedoes. German Type XIV supply U-boats or Milchkühe ("milk cows") did not have torpedo tubes or deck guns, being armed only with anti-aircraft guns for defense, and therefore could not have attacked other vessels. One character mentions sinking in a test dive. The real S-26 did not sink in a test dive, instead sinking in a collision with a patrol combatant, , in January 1942. Inaccurate portrayal of U-boat sailors The film portrays U-boat sailors machine-gunning Allied merchant crewmen who have survived their ship's sinking, so that they are not able to report the U-boat's position. In reality, U-boat crewmen are far more often known to have assisted survivors with food, directions and occasionally medical aid. Such assistance only stopped after Admiral Karl Dönitz issued the "Laconia order" following a U.S. air attack on U-boats transporting injured survivors under a Red Cross flag in 1942. German U-boat crews were thereafter under War Order No. 154 not to rescue survivors, which parallelled Allied policy. Afterward, U-boats still occasionally provided aid for survivors. In fact, out of several thousand sinkings of merchant ships in World War II, there is only one case of a U-boat's crew deliberately attacking the survivors: that of after the sinking of the Greek ship Peleus