In this dissertation, I investigated how 19th century European imperial expansion and maintenance strategies shaped imperial army recruiting and provisioning practices, which in turn shaped imperial soldier biology through the mechanism of diet. Research focused on reconstructing the longer-term and later life diets of Napoleonic and Russian soldiers. Specifically, I used stable isotope analysis of bulk collagen on the ribs and femora of soldiers from Napoleon’s Grand Army (NGA) from the mass gravesite of Šiaurės miestelis, Vilnius, Lithuania (n=53) and Imperial Russian Army (IRA) soldiers from a cemetery at Mindaugo Gatvėje, Vilnius, Lithuania (n=41). I also employed amino acid compound specific stable isotope analysis (AA-CSIA) of a subset of NGA soldiers (n=20), capturing the full range of stable carbon and nitrogen isotope values at the bulk level. The results indicate that NGA soldiers consumed more heterogenous diets prior to and during military service and more of them experienced diet shifts later in life with military service than IRA soldiers. These diet differences can be attributed to differences French and Russian imperialism. France was actively expanding through warfare during the period of study with soldiers originating from and serving in campaigns across Europe, whereas Russia was focused on maintaining its imperial borders and young men were conscripted from the core of the empire and served primarily in eastern Europe. This study demonstrates how variability in imperial strategies differentially impacts the lives of imperial soldiers, who are often overlooked in studies of imperialism.