Complex sentence: Furthermore, the Abwehr, when asked to evaluate the material, pronounced it unreliable, because until the fall of Wilhelm Canaris was secretly working against Hitler and was prepared to make the German government swallow any type of deception, such as Operation Mincemeat and Operation Fortitude.
Split into simpler sentences: Furthermore, the Abwehr, when asked to evaluate the material, pronounced it unreliable. Until the fall of Wilhelm Canaris, the Abwehr worked secretly against Hitler and was prepared to make the German government swallow any type of deception, such as Operation Mincemeat and Operation Fortitude.