The Blue Network

Keys:

• January 29, 1940 traffic

Introduction

The Blue network is closely parallel to Red one. Blue (the Lufwaffenübungsmaschinenschlüssel) lasted from October 1939 almost until the end of the war. In the early days of the war the practice traffic was indistinguishable from the operational messages, and in fact before breaks revealed the distinction between Blue and Red, Blue was believed to be the operational network. As soon as the nature of this network was discovered it had very low breaking priority and was not touched at all unless there was some reason for believing that it might have more than its usual interest.

In 1942 Blue was involved in key repeats ans was therefore broken to give assistance with other networks. Later, in 1943, some of the Cockroach traffic (including one crib), went over to Blue, and was therefore broken by this means. Most of the Blue breaks were on cribs which had at some times passed on other colours such as the Daffodil network.

It became a routine to break, if possible, a day a week to make certain the traffic was still all practice. In 1944 Blue traffic totals were very high until D-Day, but thereafter most units ceased practising. The network, however, was identifiable until 1945.