On August 26, 1805, a post chaise left the town of Mainz and rolled east toward the Rhine River. Inside the carriage sat a man, 6 English feet in height, with black corkscrew curls tumbling over his suit collar, dark flashing eyes and a black mustache. He had a handsome face, marred only by a scar on his lower jaw, the result of a bullet wound. In his hands he held a book by Marshal Charles Louis Auguste Fouquet, comte de Belle-Isle, describing the French campaign in Bohemia in 1742. On the man’s passports was the name Colonel de Beaumont.

Moving rapidly, the carriage traveled to Frankfurt, then turned southeast toward Offenbach and Wurzburg. It proceeded to the town of Bamberg on the Regnitz River. Carefully skirting the border of the Austrian empire, it followed the course of the Regnitz southward to Nuremberg. Turning east again, it rolled to the Danube, tracing that river’s course to Regensberg. There, it clattered across the Danube on the great stone bridge and continued to Passau. From there, the carriage turned west toward Munich, drove on to Ulm and through the Schwarzwald (Black Forest).

On September 10, the carriage rolled to a stop at Strasbourg, France, where Colonel de Beaumont reverted to his true identity: Joachim Murat, marshal of France, grand admiral of the empire, senator of France, governor of Paris, grand master of the cavalry…and brother-in-law of Napoleon I, emperor of the French. That same day, a succession of signal flags transmitted Murat’s coded report to Napoleon in Paris:

Sire:

I have traveled to all of the points that your Majesty ordered me to visit….I hope to furnish the different information that you required, such as the distances, the localities, the positions, the nature and states of roads and resources that exist on the communications between the principal points. I have also made notes on the principal rivers as well as the approaches to Bohemia and the Tyrol…. There exists at Wels a corps of about 60,000 men; at Braunau on the Inn, one of from 10 to 12,000, and a camp has been set up there for 30,000;…already some Austrian soldiers have arrived at Salzburg; it is generally believed that they are going to occupy Bavaria…. Prince Charles is to be the commander in Italy, and the Emperor on the Rhine. Their principal objective is to act in Italy, which appears probable given the extraordinary preparations taking place in the Tyrol….On Lake Constance there are about 15,000 men. A great number of Russians are on the frontiers of Galacia, the number is said to be 80,000 men. General Weyrother is, it is said, to be going to guide them. Finally, everything in Austria has a warlike attitude….

In Paris, at the Palace of Saint Cloud, Murat’s observations were added to those from other sources. As Napoleon studied his situation map, the red and black pins that marked the positions of French forces and their rivals revealed that an overwhelming force was gathering against France.

Largely in reaction to First Consul Napoleon Bonaparte’s coronation as emperor on December 2, 1804, on August 9, 1805, Britain, Austria, Russia, the Netherlands, Sweden, Naples and a collection of German principalities formed a new alliance against France. This Third Coalition’s objective was to force France back inside its territorial boundaries of 1789, before the French Revolution. To achieve that, the coalition planned to put more than 400,000 men into the field, far more than Napoleon could muster, and strike France from two directions.

Austria’s best general, Field Marshal Archduke Charles of Hapsburg-Lorraine, would attack in northern Italy with 94,000 men, recapture Austria’s former possessions there, then advance into southern France. Meanwhile, Austrian Archduke Ferdinand D’Este, with Quartermaster-General Karl Freiherr Mack von Leiberich as his chief of staff and mentor, would advance with 72,000 men along the Danube to discourage the elector of Bavaria from joining Napoleon and to cover the approach of Austria’s Russian allies. By October 20, the first Russian army, 50,000 men under Field Marshal Mikhail Kutuzov, would arrive, followed by another 50,000 men under Field Marshal Count Friedrich Wilhelm Büxhowden. The Russian armies would join Archduke Ferdinand and Mack for a combined invasion of northern France. To cover the two main offensives, an additional Russian force of 20,000 under General Count Levin

Bennigsen would protect the northern flank of the Danube offensive, while an additional Austrian force of 22,000 men under Archduke John would operate in the Tyrol.To distract French attention from the coalition’s main offensives, a force of 40,000 Russians, Swedes and British would advance through northern Germany into Holland, while 30,000 Russians and British would land in Naples, join with 36,000 Neapolitans and advance up the Italian Peninsula into northern Italy.

In the face of these multinational threats, Napoleon realized that his immediate project — a cross-Channel invasion of England — was now impossible. As a result of the military intelligence gathered by Murat and others, however, he had complete knowledge of the coalition’s plan. His response would be a preemptive strike into central Europe. He would try to destroy the army under Ferdinand and Mack before the Russians could arrive, then crush the Russians in turn. Meanwhile, Marshal André Masséna, with 50,000 men, would tie down Archduke Charles’ army in Italy. Marshal Guillaume Marie-Anne Brune, with 30,000 men, would forestall the coalition advance into Holland, and Général de Division Laurent Gouvion St. Cyr, with 18,000, would march on Naples to prevent any coalition advance there.

The instrument for Napoleon’s offensive against Ferdinand and Mack stood at Boulogne on the English Channel. His Grande Armée, 180,000-strong, highly trained, well armed and mobile, was ready for action.

The Grande Armée was divided into seven corps, each commanded by a marshal of France. Jean Baptiste Bernadotte commanded the I Corps; Auguste-Fredéric-Louis Marmont, the II Corps; Louis-Nicholas Davout, the III Corps; Jean-Baptiste de Dieu Soult, the IV Corps; Jean Lannes, the V Corps; Michel Ney, the VI Corps; and Pierre Franois Charles Augereau, the VII Corps. Joachim Murat commanded the Cavalry Reserve. The seven corps, Cavalry Reserve and Imperial Guard under Napoleon’s own hand totaled 145,000 infantry and 38,000 cavalry; to this would be added 25,000 Bavarian allies.

On August 27, the Grande Armée broke camp and marched east. Bernadotte’s I Corps, stationed at Hanover, headed for Wurzburg to collect the Bavarians, while the other six corps converged on the Rhine. Napoleon believed that ‘The force of an army…is the sum of its mass multiplied by its speed.’ The distance from Boulogne to the Rhine is 450 miles, and each soldier covered it on foot, carrying his knapsack and musket, a total of 65 to 75 pounds. The price was high. Jean Roch Coignet, a private in the Foot Grenadiers of the Imperial Guard, recalled: ‘Never was there such a terrible march. We had not a moment for sleep, marching by platoon all day and all night, and at last holding onto each other to prevent falling. Those who fell could not be awakened. Some fell into the ditches. Blows with the flat of the sabre had no effect upon them. The music played, the drums beat a charge; nothing got the better of sleep….’

On September 26, the ‘torrents’ of the Grande Armée crossed the Rhine. The march continued into Germany until after wheeling to the south on October 6, the army found itself in line along the Danube from Ulm to Ingolstadt. Napoleon’s army was now farther east than the unsuspecting army of Ferdinand and Mack, which had imprudently advanced along the Danube to Ulm in Bavaria. By the time the Austrians realized what was happening and struck north to attack the French, it was too late. The Austrian army was encircled, driven into Ulm and surrounded. On October 20, Mack and 27,000 surviving Austrian soldiers laid down their arms. Ferdinand, with 6,000 cavalry, managed to escape. As the French soldiers marched away from Ulm they sang: