concepts In the French Revolutionary and Napoleonic Wars, new techniques stressed the division of armies into all-arms corps that would march separately and only come together on the battlefield. The less-concentrated army could now live off the country and move more rapidly over a larger number of roads. Fortresses commanding lines of communication could be bypassed and would no longer stop an invasion. Since armies could not live off the land indefinitely, Napoleon Bonaparte always sought a quick end to any conflict by pitched battle. This military revolution was described and codified by Clausewitz. Industrial advances Advances in artillery made previously impregnable defences useless. For example, the walls of Vienna that had held off the Turks in the mid-17th century were no obstacle to Napoleon in the early 19th. Where sieges occurred (such as the siege of Delhi and the siege of Cawnpore during the Indian Rebellion of 1857), the attackers were usually able to defeat the defences within a matter of days or weeks, rather than weeks or months as previously. The great Swedish white-elephant fortress of Karlsborg was built in the tradition of Vauban and intended as a reserve capital for Sweden, but it was obsolete before it was completed in 1869. Railways, when they were introduced, made possible the movement and supply of larger armies than those that fought in the Napoleonic Wars. It also reintroduced siege warfare, as armies seeking to use railway lines in enemy territory were forced to capture fortresses which blocked these lines. During the Franco-Prussian War, the battlefield front-lines moved rapidly through France. However, the Prussian and other German armies were delayed for months at the siege of Metz and the siege of Paris, due to the greatly increased firepower of the defending infantry, and the principle of detached or semi-detached forts with heavy-caliber artillery. This resulted in the later construction of fortress works across Europe, such as the massive fortifications at Verdun. It also led to the introduction of tactics which sought to induce surrender by bombarding the civilian population within a fortress, rather than the defending works themselves. The siege of Sevastopol during the Crimean War and the siege of Petersburg (1864–1865) during the American Civil War showed that modern citadels, when improved by improvised defences, could still resist an enemy for many months. The Siege of Plevna during the Russo-Turkish War (1877–1878) proved that hastily constructed field defences could