Railroad
AMSCO p. 313 and 398
..The railroads offered new strategic opportunities. Troops could be transported six times as fast as the armies of Napoleon [1808–1812] had marched, and the fundamentals of all strategy, time and space, appeared in a new light. A country which had a highly developed system of rail communications gained important and possibly decisive advantages in warfare. The speed of the mobilization and of the concentration of armies became an essential factor in strategic calculations. In fact, the timetable of mobilization and assemblage, together with the first marching orders, henceforth formed the very core of the strategic plans drawn up by the military staffs in expectation of war ...
​
Source: Source: Hajo Holborn, “Moltke’s Strategical Concepts,” Military Affairs (General Moltke believed railroads would contribute to Otto von Bismarck’s Prussian military efforts in the 1860s.)
​