Sieges were at least as important as battles in the wars fought between 1815 and 1914. The Crimean War pivoted on the siege of Sevastopol; Vicksburg was the foil to Gettysburg in the campaign of 1863; and in 1877 the Russian invasion of European Turkey was halted at Plevna. For military theorists the wars of German unification embodied the notion of decisive maneuver leading to victory on the battlefield. And yet in all three, sieges or their threat played decisive roles in the outcome. In 1864 the Prussians invested the Danes at Duppel; in 1866 they preferred to settle with the Austrians after Sadowa rather than lay siege to Vienna; and in 1870 the resistance of Metz and, above all, Paris prolonged the war and confounded Helmuth von Moltke. The two wars that immediately preceded the outbreak of World War I, both of them closely studied by European military observers, told a similar story: The siege of Port Arthur formed the centerpiece of the Russo-Japanese War, and the defense of Adrianople constituted the heart of the Ottoman empires efforts to resist the encroachments of Bulgaria in the First Balkan War.

In the 1880s the existing fortifications of Europe, constructed of bricks and mortar and sited close to the cities and localities they were designed to defend, were confronted with almost instantaneous obsolescence. The combination of high explosive, smokeless powder, and delayed-action fuses increased the range and penetrative power of heavy artillery. France, which had just spent 660 million francs on the construction of 166 forts, 43 secondary works, and 250 batteries in a defensive scheme for the eastern frontier, almost dropped out of the race rather than compete.