The campaigning season of 1914 was the shortest of any year of the war, but it built the framework for much that followed. Starting in the first days of August, armies mobilized according to prewar plans: reservists were called up; field armies were moved to national borders. War plans ceased to be documents on paper, previewed in peacetime maneuvers: they now became the guidelines for military operations. Each of the major warring nations had a war plan, although some were both more elaborate and more ambitious than others. During the first weeks—and perhaps the first months—of the war, while the conflict offered a host of surprises, much of the fighting took place along the lines of prewar expectations. Germany invaded France through Belgium; the British Expeditionary Force (BEF), the bulk of the British army, crossed the Channel to serve alongside the French army; Russian forces invaded both eastern Germany and the northern parts of the Austrian empire; Austrian forces marched into Serbia. The generals of the time operated on the basis of principles derived from the wars of Napoleon. They directed their efi'orts toward a quick and decisive defeat of the enemy's main forces. Their tool was the powerful and determined offensive. As one authority on warfare had put it in 1905, "The essence of successful leadership in the future will be ... a rapid and sustained advance which will overrun all opposition by its very momentum." 12 The vast changes in the size and composition of armies, the equally great alterations in the technology of weapons, in means of transportation, and in tools of communication had not altered such thinking—at least not at the top of the military ladder. In the American Civil War (1861-1865), the Boer War (1899-1902), and the Russo-Japanese War (1904-1905), bold and bloody offensives had not lived up to expectations derived from the time of Napoleon. But Europe's military leaders had not chosen to alter their plans. Instead, they used recent European experience, such as the decisive success of Prussian arms in the Franco-Prussian War (1870-1871), as the norm. As Jay Luvaas has pointed out in regard to the events in North America, "Most of those who studied the Civil War after 1 870 were in reality seeking to confirm accepted principles rather than to discover new infor mation that might lead to a change in doctrine." 1 3 Plans based on the old doctrine of the bold and decisive offensive now had their time of testing.