The History and Mathematics of Codes and Code Breaking

The Morality of Admiral Hall’s Actions

Upon learning the intended plans of the Germans from deciphering the Zimmerman telegram, it was ethical of Admiral Hall to withhold such information from the President.


One may argue that Admiral Hall should morally concede the information to the President so that Britain may be subsequently informed, and lives could be potentially saved during the outbreak of unrestricted submarine warfare. Yet, if America was to intervene before German acted out their plan, they would’ve “concluded that their method of encryption had been broken,” leading them to “develop a new and stronger encryption system” (Singh 113). This grants the possibility of the German’s using an extremely more complicated encryption system, one that the cryptanalysts in Britain’s Room 40 may never solve in their lifetime, to act out their unrestricted submarine warfare unopposed. This, in turn, could’ve led to a higher number of wartime casualties, especially among passenger ships. Thus, through decrypting future German telegrams without their knowledge that their encryption system had already been broken, Admiral Hall’s actions could potentially save many more lives than he would’ve had he passed on the information.


Furthermore, as history proved, by not informing the President, Admiral Hall ensured that the Germans did not realize the Americans had broken their encryption system, granting the Americans an advantage in decrypting any future German messages encrypted by the same system. Eventually the Mexican version of the Zimmermann telegram led America to retaliate, granting the same outcome had the Admiral actually passed on the information, but without the Germans discovering their blunder.


Sacrifice Few to Save Many


Strategical rather than unethical


  1. strutte

    You raise a good point that, even though he knowingly withheld info from the US, Admiral Hall’s decision prevented Germany from creating an even more difficult cipher with (more or less) the same end result that would have arisen if he had shared the information. I agree with you that Hall had good intentions in keeping this information secret in order to more easily decipher future intercepted information. That being said, how was he to know that Germany would not have changed their encoding mechanisms on their own, and why was it ethical for him to risk lives without guarantee that it would save more in the future?

    • Derek

      Great point, Emily. Hall was making a decision based on a number of assumptions, a key one being, as you note, that the Germans would continue using the same encryption methods until they knew them to be broken. As it turned out, that was a correct assumption, but Hall couldn’t have known that for sure at the time.

      One could argue that by telling the Americans, Hall would definitely save lives. By not telling them, he was only probably saving lives. Tough call.

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