In 1974 Group Captain Frederick Winterbotham shocked the world when he revealed in his semiautobiographical work, The Ultra Secret, that the Allies had been breaking high-grade German ciphers throughout the greater portion of the Second World War in an effort commonly referred to as ULTRA.1 His disclosure sparked a tempest as historians anticipated that his admission would lead to a major revision of Second World War historiography. At first, what promised to be a new vista for historical research soon turned into a quagmire. When the British Government selectively released files pertaining to ULTRA, only messages sent to commands in the field were originally released whereas the supporting documents necessary to properly assess and interpret the impact of ULTRA in general, and on Army Group, Army and Corps commanders and their subordinates in the field in particular, were retained. As a result, the reassessment of this aspect of military history met a similar fate to that of British armour at the foot of Verrières-Bourgébus ridge during Operation Goodwood—very good initial progress followed by confusion and lack of consolidation resulting in the perception that ULTRA was nothing more than a highly overrated white elephant. Two decades later, Government Communication Headquarters (GCHQ) in the UK wisely reviewed their policy and began a protracted release of millions of pages of material to coincide with the 50th anniversary of the end of the Second World War. Included were materials that shed new light on the production and dissemination of ULTRA (at Bletchley Park) and its employment by the consumer, Allied High Command, in the field.2 The releases have thus far included everything from security regulations for the handling of messages, to classified inhouse accounts of the impact of ULTRA on commands, to high-level policy papers and distribution lists to name but a few. In addition to the ULTRA material, formerly classified Intelligence summaries (produced at each level of command from Eisenhower’s Supreme Headquarters down to brigade level) were also declassified during this period providing the historian with two mutually supporting sources to layer upon the existing corpus of material.3 As a result, new insight and further understanding can be achieved concerning intentions, orders, decisions and operations that may have been regarded, at that time or since, as peculiar, questionable or ill-conceived. The impact of these new releases on the historiography of Canada’s role in the Second World War can be witnessed in part by re-examining the costly and seemingly questionable advance by the Black Watch (Royal Highland Regiment) of Canada on May-sur-Orne during the afternoon of 5 August 1944.