The American Civil War presented an exceptional state of affairs in modern warfare, because strong personalities could embed their own command philosophies into field armies, due to the miniscule size of the prior US military establishment. The effectiveness of the Union Army of the Tennessee stemmed in large part from the strong influence of Ulysses S. Grant, who as early as the fall of 1861 imbued in the organization an aggressive mind-set. However, Grant’s command culture went beyond simple aggressiveness – it included an emphasis on suppressing internal rivalries among sometimes prideful officers for the sake of winning victories. In the winter of 1861 and the spring of 1862, the Army of the Tennessee was organized and consolidated into a single force, and, despite deficits in trained personnel as compared to other Union field armies, Grant established important precedents for both his soldiers and officers that would resonate even after his departure to the east. The capture of Vicksburg the following summer represented the culminating triumph of that army, cementing the self-confident force that would later capture Atlanta and win the war in the western theater.

German military history of 1871 to 1945 is often seen as a direct continuation of Prussian military history. Taking a closer look at the organizational and cultural background of German military forces produces a slightly more nuanced picture and makes it possible to divide the history of the German Army into five phases. Initially, the German Empire effectively had four different forces – the Prussian, Bavarian, Saxon, and Württemberg armies – united only in times of war. During the First World War, these German "armies" increasingly lost their prewar independence, while the war itself had a unifying effect on German society and on its armed forces. Following the defeat of 1918, the army of the newly founded Weimar Republic was developed as a small, elite force exclusively based on Prussian traditions. The 1936 rearmament then turned this force into a mass army, the Wehrmacht, which, while still sticking to Prussian traditions, struggled with various issues caused by rapid expansion. Finally, during the Second World War, the Wehrmacht evolved from a purely German force into one in which significant numbers of foreigners from all over Europe served as volunteers, resulting in an army transcending the boundaries of the nation-state.