Napoleon had set up a camp at Boulogne-sur-Mer to prepare for an invasion of Britain after Great Britain broke the Peace of Amiens and declared war on France in May 1803.

By 1805, Britain has convinced Austria and Russia to join a Third Coalition against France.

Napoleon has assembled an invasion force, called the Armée d'Angleterre (Army of England) around six camps at Boulogne.

He intends to use this invasion force to strike at England, and is so confident of success that he has commemorative medals struck to celebrate the conquest of the English.

Napoleon knows the French fleet cannot defeat the Royal Navy in a head-to-head battle and plans to lure it away from the English Channel.

The French Navy would escape from the British blockades of Toulon and Brest and threaten to attack the West Indies, thus drawing off the British defense of the Western Approaches, in the hope a Franco-Spanish fleet could take control of the channel long enough for French armies to cross from Boulogne and invade England.

However, after defeat at the naval Battle of Cape Finisterre in July 1805 and Admiral Villeneuve's retreat to Cadiz, invasion will never again be a realistic option for Napoleon.

Although they never invade, Napoleon's troops receive careful and invaluable training for any possible military operation.

Boredom among the troops occasionally set in, but Napoleon pays many visits and conducted lavish parades in order to boost morale.

He also orders his soldiers to be vaccinated.

The men at Boulogne formed the core for what Napoleon will later call La Grande Armée.

At the start, this French army has about two hundred thousand men organized into seven corps, which are large field units that contain thirty-six to forty cannon each and are capable of independent action until other corps can come to the rescue.

A single corps (properly situated in a strong defensive position) can survive at least a day without support, giving the Grande Armée countless strategic and tactical options on every campaign.

In addition to these forces, Napoleon has created a cavalry reserve of twenty-two thousand organized into two cuirassier divisions, four mounted dragoon divisions, one division of dismounted dragoons and one of light cavalry, all supported by twenty-four artillery pieces.

By 1805, the Grande Armée has grown to a force of three hundred and fifty thousand men, who sre well equipped, well trained, and led by competent officers.