In the late 1940s, the Department of National Defence enthusiastically embraced microfilming technology, undertaking a massive project to microfilm several million files covering the period 1885 to 1948. This article describes the authors’ research to trace one particular microfilm job covering Military Personnel Files managed by the Department of Militia and Defence. The authors have unearthed a large cache of unexplored records, comprising tens of thousands of military personnel files, the majority of which deal with military service during the Great War.