The article focuses on the history of the Russian army in imperial context, in particular, on “national” and regional component within the imperial army, its formation throughout the process of imperial extension, its role in both defense and internal government of the empire and problems that heterogeneous composition of the imperial army posed for the empire’s integrity and military management. The author starts with an observation that the Russian imperial army lacked uniformity, suggesting that this was a persistent factor of Russian military history from the 16th century (Cossacks and the Tatar regiments) until the end of the ancien regime. The author devises a typology of national and irregular regiments, which complemented the main regular forces recruited from the empire’s “titular nationality.” The first type was represented by the armed forces of the autonomous regions of the empire (the Kingdom of Poland, the Grand Duchy of Finland) and Russia’s protectorates in Central Asia (Bukhara and Khiva). A short lived Lithuanian Corpus falls within this category for it was dominated by the Polish element and its fate was tied to the history of the army of the Kingdom of Poland. The author concludes that that type of military formations mainly served to articulate the political autonomy of respective regions and nationalities but their military efficacy and political loyalty were doubtful. The second type was represented by “national” regiments, which constituted a part of the regular army but were recruited from a particular region or people of one nationality. The most representative examples include the Cavalry-Muslim regiment, Daghestani Cavalry regiment, the Crimean-Tatar Squadron. Those regiments were part of the internal policy of cooptation of the borderland elites into the imperial elite, their special status and continuity with the indigenous traditions (very often that of nomad way of life and war) lessened the harsh effect of integration of respective borderland nationalities into the Russian imperial society and state. They were also used as a valuable asset for regional wars, in particular, the Caucasian war. The third type consisted of irregular national formations, namely the Cossacks and militia recruited from non-Russian nationalities. They were usually necessitated by the military needs of the empire during the extensive and arduous campaigns, such as the war of 1812, the Crimean war, and the Russo-Turkish wars of 1828–1829 and 1877–1878. A subsection is devoted to the history of the Cossack forces, which are viewed from the viewpoint of their multiethnic character and role as frontier guard and settlers. The author concludes that the heterogeneous structure of the Russian imperial armed forces served the varying needs of the empire, which engaged in both interstate and regional (within the empire) war efforts. The article demonstrates that the history of the imperial army should not be viewed only from the viewpoint of its defense function. In fact the army was an important tool for internal imperial government. One aspect of the latter is the role that non-Russian military regiments played in symbolic representations of the Russian monarchy and government, epitomizing imperial diversity in unity.