Inside Room 40: The Codebreakers of World War 1

When the German cruiser Magdeburg ran aground off the Estonian coast in August 1914, the British Admiralty did not realize that what was onboard the ill-fated vessel would hand them a decisive advantage in the battle for North Sea supremacy, and subsequently lead to the birth of the Government Communications Headquarters. Before long, the codebooks used by German warships, u-boats, and naval zeppelins, and the ciphers used by the Germans to communicate with their naval attachés and embassies, had also fallen into the Admiralty’s possession. Having been gifted such priceless information, Admiral Oliver, the Director of Naval Intelligence, assembled a team comprising the most talented British cryptologists who, by the end of the war, had deciphered over 15,000 German communications. Operating out of their humble base in Room 40 of the Admiralty Headquarters, and led by Alfred Ewing, who constructed ciphers as a hobby, the team played an integral role in the naval engagements during the war.