Cryptography and the World Wars: The History of Codemaking and Codebreaking during Both Global Conflicts

World War I was the first major conflict in which new electronic means of transmitting and receiving messages became a major factor in political and military operations. The electric telegraph was developed in the first half of the 19th century, and by 1850, there were several telegraph companies around the world providing a service that allowed virtually instantaneous communication over long distances. This was a major breakthrough, but the telegraph depended on the availability of wires to transmit messages between stations, meaning that if these wires were broken or damaged, communications were cut off. Of course, this came with a fundamental problem: radio, telephone, and telegraph messages could be intercepted by the enemy, potentially giving them notice of impending operations. To protect these electronic messages from being read by the enemy, armies began to use codes and ciphers to disguise the meaning of messages. Teams were created to devise effective codes and ciphers, and these were quickly followed by other teams whose role was to attempt to break the codes and ciphers used by the other side. As a result, a secret war began, almost completely hidden from public view, as the belligerents devised complex ways of hiding the real meaning of their own messages while simultaneously attempting to understand those of the enemy. During the Second World War, cryptography suddenly became a significant factor in warfare because of mid-20th century advances in communications technology. With radios small and common enough to be fitted into most individual vehicles and readily carried in a man-portable form, information and orders flowed from supreme headquarters to individual squad leaders, tanks, and soldiers at the front and back again. Despite the power of the new technology and its metamorphic effects on warfare, cryptography's story during World War II remained a very human one.