This procedure was used by "Wehrmacht" and "Luftwaffe" only. The "Kriegsmarine" procedures on sending messages with the Enigma were far more complex and elaborate. Prior to encryption the message was encoded using the "Kurzsignalheft" code book. The "Kurzsignalheft" contained tables to convert sentences into four-letter groups. A great many choices were included, for example, logistic matters such as refuelling and rendezvous with supply ships, positions and grid lists, harbour names, countries, weapons, weather conditions, enemy positions and ships, date and time tables. Another codebook contained the "Kenngruppen" and "Spruchschlüssel": the key identification and message key.