One of the most interesting historical sections so far in David Khan’s The Code-Breakers describes the campaign in North Africa during WWII. Because of a spy working in the US embassy in Rome, the American BLACK code and its accompanying superencipherment tables were stolen. This had a number of major tactical impacts, because it allowed Rommel to read the detailed dispatches being sent back by the American military attache in Cairo.
Khan argues that this intelligence played a key role in Rommel’s critical search for fuel. His supply line across the Mediterranean was threatened by the British presence in Malta. Knowledge about a major resupply effort allowed him to thwart commando attacks against his own aircraft and turn back two major resupply convoys. It also provided vital information on Allied defences during his push towards Suez.
The loss of Rommel’s experienced cryptographers due to an accidental encounter with British forces had similarly huge consequences. It cut off the flow of intelligence, both because of changed codes and loss of personnel. As a result, the Allied assault at Alamein proved to be a surprise for Rommel and an important turning point.
As with so many examples in warfare, this demonstrates the huge role of chance in determining outcomes. Had security been better at the embassy in Rome, Rommel might have been stopped sooner. Had the German tactical intelligence team not been intercepted, Rommel might have had detailed warnings about Alamein. The example also shows how critical intelligence and cryptography can be, in the unfolding of world affairs.