The Battle of Rossbach took place on 5November 1757 during the Third Silesian War (1756–1763, part of the Seven Years' War) near the village of Rossbach (Roßbach), in the Electorate of Saxony. It is sometimes called the Battle of, or at, Reichardtswerben, after a different nearby town. In this 90-minute battle, Frederick the Great, king of Prussia, defeated an Allied army composed of French forces augmented by a contingent of the Reichsarmee (Imperial Army) of the Holy Roman Empire. The French and Imperial army included 41,110 men, opposing a considerably smaller Prussian force of 22,000. Despite overwhelming odds, Frederick managed to defeat the Imperials and the French.

The Battle of Rossbach marked a turning point in the Seven Years' War, not only for its stunning Prussian victory, but because France refused to send troops against Prussia again and Britain, noting Prussia's military success, increased its financial support for Frederick. Following the battle, Frederick immediately left Rossbach and marched for 13 days to the outskirts of Breslau. There he met the Austrian army at the Battle of Leuthen; he employed similar tactics to again defeat an army considerably larger than his own.

Rossbach is considered one of Frederick's greatest strategic masterpieces. He crippled an enemy army twice the size of the Prussian force while suffering negligible casualties. His artillery also played a critical role in the victory, based on its ability to reposition itself rapidly responding to changing circumstances on the battlefield. Finally, his cavalry contributed decisively to the outcome of the battle, justifying his investment of resources into its training during the eight-year interim between the conclusion of the War of Austrian Succession and the outbreak of the Seven Years' War. The Franco-Austrian defeats in the European theater prompted military reforms in both France and Austria.

Seven Years' War

Although the Seven Years' War was a global conflict, it took a specific intensity in the European theater based on the recently concluded War of the Austrian Succession (1740–1748). The 1748 Treaty of Aix-la-Chapelle concluded the earlier war in which Prussia and Austria were a part; its influence among the European powers was little better than a truce. Frederick II of Prussia, known as Frederick the Great, acquired the prosperous province of Silesia, but had wanted much of the Saxon territories as well. Empress Maria Theresa of Austria had signed the treaty to gain time to rebuild her military forces and forge new alliances; she was intent upon regaining ascendancy in the Holy Roman Empire.Peter H. Wilson, The Heart of Europe: A History of the Holy Roman Empire. Penguin, 2016, pp. 478–479. By 1754, escalating tensions between Britain and France in North America offered the Empress the opportunity to regain her lost Central European territories and to limit Prussia's growing power. Similarly, France sought to break the British control of Atlantic trade. France and Austria put aside their old rivalry to form a coalition of their own. Faced with this sudden turn of events, the British king, George II, aligned himself with his nephew, Frederick, and the Kingdom of Prussia; this alliance drew in not only the British king's territories held in personal union, including Hanover, but also those of his and Frederick's relatives in the Electorate of Hanover and the Landgraviate of Hesse-Kassel. This series of political maneuvers became known as the Diplomatic Revolution.D.B. Horn, "The Diplomatic Revolution" in J. O. Lindsay, ed., The New Cambridge Modern History vol. 7, The Old Regime: 1713–63 (1957): pp. 449–464; Jeremy Black, "Essay and Reflection: On the 'Old System' and the Diplomatic Revolution' of the Eighteenth Century", International History Review (1990), 12:2 pp. 301–323.

Situation in 1757 At the start of the war, Frederick had one of the finest armies in Europe: his troops—in any company—could fire at least four musket volleys a minute, and some of them could fire five; his army could march a day, and was able to conduct, even under fire, some of the most complex maneuvers known.Fred Anderson, Crucible of War: The Seven Years' War and the Fate of Empire in British North America, 1754–1766. Knopf Doubleday Publishing Group, 2007, p. 302. After overrunning Saxony, Frederick campaigned in Bohemia and defeated the Austrians on 6May 1757 at the Battle of Prague. Initially successful, everything after the Battle of Kolín, went awry: what had started as a war of movement by Frederick's agile army turned into a war of attrition.Blanning, p. 232.

By summer 1757, Prussia was threatened on two fronts. In the east, the Russians, under Field Marshal Stepan Fyodorovich Apraksin and William Fermor, besieged Memel with 16,000 troops . Memel had one of the strongest fortresses in Prussia, but after five days of artillery bombardment, the Russian army successfully stormed it.Robert B. Asprey, Frederick the Great: The Magnificent Enigma. Ticknor & Fields, 1986, p. 460. The Russians then used Memel as a base to invade East Prussia and defeated a smaller Prussian force in the fiercely contested Battle of Gross-Jägersdorf on 30 August 1757. However, the Russians were unable to take Königsberg, the capital of East Prussia, after using up their supplies of cannonballs at Memel and Gross-Jägersdorf, and retreated soon afterward. The logistics of supplying a large army remained a problem for the Russians throughout the war.Daniel Marston, The Seven Years' War, London; Osprey, 2001, p. 22. Although previous experiences in wars with the Ottoman Empire had exposed these problems, the Russians had not solved the challenge of supplying their army at a distance from Moscow.David Stone, A Military History of Russia: From Ivan the Terrible to the War in Chechnya, New York; Praeger, 2006, p. 70 Even so, the Imperial Russian Army offered a new threat to Prussia, forcing Frederick to abandon his invasion of Bohemia and to withdraw further into Prussian territory.Anderson, p. 176.

In Saxony and Silesia, the Austrian forces slowly reclaimed territory held by Frederick earlier in the year. In September, at the Battle of Moys, Prince Charles's Austrians defeated the Prussians commanded by Hans Karl von Winterfeldt, one of Frederick's most trusted generals, who was killed in the battle.Anderson, p. 302. As summer ended, a combined force of French and the Reichsarmee (Imperial Army) troops, approaching from the west, intended to unite with Prince Charles's main Austrian force, which itself advanced west to Breslau. Prince Soubise and Prince Joseph of Saxe-Hildburghausen shared command of the Allied force.Marston, p. 41.

If these armies were to unite, Prussia's situation would be dire indeed. Recognizing this threat, Frederick used the strategy of interior lines to advance in a quick, arduous march reminiscent of the forced marches of his great-grandfather, Frederick William I, the "Great Elector". An army marches only as fast as its slowest components, which are usually the supply trains, and Frederick obtained needed supplies ahead of the army, which enabled him to abandon his supply wagons. His army covered in only 13 days. Bringing his enemy to battle proved difficult, as the Allies flitted out of his reach. Both Frederick and his enemies moved back and forth for several days, trying to maneuver around each other but ending up in a stalemate. During this time, an Austrian raiding party attacked Berlin and almost captured the Prussian royal family.

Terrain and maneuvers The story of the Battle of Rossbach is as much the story of the five days of maneuvering, leading to the battle as it is of those famous 90 minutes of battle, and the maneuvers that were shaped by the terrain. Initial activity focused on the village of Weissenfels, where the middle Saale emerges from the Buntsandstein of the Thuringian Basin in the Leipzig highlands, not far from the modern-day A9 highway. Parts of the valley between Leipzig and Saale were relatively narrow, cut by the river and its tributaries; the hillsides were steep, with limited river crossings; this influenced the troop movements leading to the battle, as the various armies competed for sites to cross the river.J. F. C. Fuller, A Military History of The Western World, Vol. II: From the Defeat of the Spanish Armada to the Battle Of Waterloo, Da Capo Press, 1987 pp. 202–203.

The scene of the battle at Rossbach, lay southwest of Merseburg, on a wide plateau dotted by hillocks with elevations up to .The elevation of Rossbach is . Braunsbedra and Reichardtswerben are the two closest villages, and their elevations above sea level are and respectively. Flood Maps of Germany. Elevation of Braunsbedra, German flood maps. 2014. Accessed 16 August 2017. The locale was a wide plain largely without trees or hedges. The ground was sandy in some areas, and marshy in others; a small stream ran between Rossbach and Merseburg, south of which rose two low hills, the Janus and the Pölzen. Thomas Carlyle later described these as unimpressive, although certainly horses dragging cannons would notice them, as the animals slipped in loose stones and sand. To the west, the Saale flowed past a small town of Weissenfels, a few miles southeast of Rossbach.

On 24 October, the Prussian Field Marshal James Keith was in Leipzig when the Imperial Army occupied Weissenfels. Frederick joined him there two days later. Over the next couple of days, the King's brother, Prince Henry, arrived with the main body of the army and his brother-in-law, Duke Ferdinand of Brunswick-Wolfenbüttel, arrived from Magdeburg. Prince Moritz of Anhalt-Dessau arrived by 28 October; although his men had marched up to in a day, they were still eager to face the Allied forces, who had established a post close to Markranstädt, and maintained some line of control along the Saale river.Herbert J. Redman,Frederick the Great and the Seven Years' War, 1756–1763. McFarland. 2015, p. 123. This gave Prussia a complement of 22,000 men. Gaston Bodart, Militär-historisches Kriegs-Lexikon, (1618–1905). Vienna, Stern, 1908, p. 220. On 30 October, the King led the army out of Leipzig, toward Lützen, with Colonel Johann von Mayr and his Freibatallion, an independent unit of 1,500 mixed troops, in the lead to flush out Allied pickets and reconnaissance parties; this cleared the way for the main army. The next day, Frederick moved out of Lützen at 3:00 pm, during heavy rain. Despite the weather, the Széchenyi Hussars harassed their line of march, but, in the hussars' eagerness to annoy the Prussians, they forgot to send a messenger to Weissenfels to warn the garrison of the Prussian approach. When Mayr appeared at about 8:00 a.m. on the 31st, followed by the King and the rest of his army, the French were completely surprised. The force there consisted of four battalions and 18 companies of grenadiers, all but three of them French: 5,000 men under command of Louis, Duke de Crillon.

Crillon closed up the town and prepared for action. The Prussians unlimbered their artillery and fired on the town gates; Mayr's men and the Prussian grenadiers knocked out the obstructions. A few precise hits cleared their way into the town and the Allied resistance disappeared in cannon smoke; the Allied troops rapidly withdrew from the town across the bridge over the Saale and, as they withdrew, they set fire to the bridge to prevent the Prussians from following them. A conflagration consumed the wooden bridge so rapidly that 630 men, most of the garrison, were trapped on the wrong side. They surrendered with their arms and equipment. Saxe-Hildburghausen, at Burgwerben, ordered a barrage laid down across the Saale to prevent the Prussians from repairing the bridge. Frederick's gunners responded in kind and the two shelled each other until about 3:00 pm.Redman, pp. 123–124.