It is extremely hard to discern whether or not Admiral Hall's decision to withhold the information contained in the Zimmerman Telegram from America is ethical or not. At first, it seems selfish to let Americans die because they are blind to the Germany and its allies' aggression towards them, especially from an American's perspective just so Britain can maintain the secret that they can decode German messages. But, sometimes I believe it is ethical to sacrifice the lives of a few to save the many. If it were not for Britain's strategic move to steal the unencrypted message that the President of Mexico received in order to conceal their cryptanalysis breakthrough, Germany may have created a different, more secure code that could have prolonged the war. This prolonging of the war would have ultimately led to more death than if Britain hid the fact that they were able to break Germany's code and use it to their advantage in thwarting Germany's advances. As an American, it is hard to accept the fact that Britain had the technology at its disposal to save some American lives during the war, but you have to look at the long term effects. Saving those American lives could have easily prolonged the war and costed the Allies many more fatalities, so I believe Britain made its decision based on the greater good of the Allies and made the ethical choice.