Complex sentence: Max Newman devised a decision tree and then set Jack Good and Donald Michie the task of devising others that were then used by the Wrens without recourse to the cryptanalysts if certain criteria were met.
Split into simpler sentences: Max Newman devised a decision tree and then set Jack Good and Donald Michie the task of devising others. These were used by the Wrens without recourse to the cryptanalysts if certain criteria were met.