Nearly 100 years ago, the US Army and its international partners committed a task force in 1918 to northern Russia while simultaneously conducting large scale combat operations in western Europe during World War I. Like many modern expeditionary operations in the last ten years, the Allies in north Russia operated in a hostile environment with ill-defined problems in an immature theater of operations. Since there are similarities between the Allied expeditionary force of 1918 in north Russia and US expeditionary operations in the last decade, a case study focused on the operational approach of the Allied Expeditionary Forces North Russia (AEFNR) may identify lessons for operational planners and commanders to consider in future expeditionary operations. To identify these lessons, this monograph first reviews the origins and definitions of operational art. Next, the case study of the AEFNR shows that the expedition's commanders exercised operational art through an approach based on their understanding of the strategic and operational environments. In the end, the monograph discovers three lessons from the expedition based on critiques from various leaders that are still important for operational planners to consider today.