Why Enigma decryption gives only part of the intelligence history

Clarke argues that published Enigma research leaves part of the wider signals-intelligence history unexplained. He connects the lower visibility of traffic-analysis methods with their continued military value and their relationship to communications equipment. Declassified American complaints about British conclusions from apparently similar data support his inference that important methods remained undisclosed. Those complaints are described without identifying the documents in this passage. His own writing on Huff-Duff drew objections both for including the subject and for explaining too little. The technical account stopped where he could no longer find sources adequate to support further detail. That is a limit on his available research, rather than a complete inventory of what had been released.