1803- 1805 War with the French Empire:

In May 1803 the British Empire declared war on France, because the French army occupied Switzerland and Piemont. The invasion army of Emperor Napoleon I still stood at the Channel and waited for the beginning of the operation against the English. Nelson became Commander in Chief of the Mediterranean Fleet. He started the blockade of Toulon. In 1804, English secret agents reported to Nelson Napoleon's plan for his fleet:

"The French Mediterranean Fleet has orders to break the blockade of Toulon and sail through the Strait of Gibraltar. After arriving in the Atlantic Ocean they should sail towards the West Indies. Of course the British will send a squadron there to destroy this French danger. But after its arrival the fleet has to sail immediately back to Europe and unify with Spanish squadrons and French ships from the Atlantic ports. If possible, Dutch ships should also join the Allied Armada.

After the unification of all allied forces, the Armada is to enter the Channel and destroy all English ships. Its main task is it to keep control of the Channel until the invasion forces have entered the British Isles.

The first part of Napoleon's plan is the most important one. Due to the French ships sailing in the direction of the West Indies, the British have to send ships out to find and destroy the French ships, which can be a danger to the British colonies in the West Indies. So the defence of the Channel becomes weaker and the invasion-forces are able to cross the Channel."

Napoleon's Orders:
Napoleon ordered Vice-admiral Villenneuve to become Commander in Chief of the Armada. Nelson took this danger very seriously, although the French Navy wasn't as powerful and trained as the British one, because they were blockaded in their ports and couldn't sail out for training. Nelson invented a special tactic to defeat the French plan. He gave the French enough free sea space to leave Toulon, and then he wanted to follow the French to the West Indies and try to destroy them with a reinforced fleet. He had some advantages because he knew the French plan.

Finally in the night of the 30th March 1805, the French fleet left Toulon for the West Indies. Before crossing the Atlantic Ocean the French fleet was reinforced by parts of the Royal Spanish Navy. Nelson lost the contact, later British frigates informed Nelson about the French route. Nelson now sailed towards the West Indies, but he missed the French fleet. Nelson followed the French with a three day distance.

On 4th of June, the French fleet got in contact with a British supply convoy. Of course the French had more ships and so they captured 14 ships and destroyed some of the escort ships. 22nd of July the French-Spanish Armada arrived Ferrol and was supplied by the Spanish navy base there. Nelson controlled Cadiz, one of the biggest Spanish naval ports. He ordered his fleet to control Brest, the most important French navy base at the Atlantic Ocean. Both times the results were negative and he sailed back to England dissatisfied and waited for further messages of the French ships.

Calder Ordered Home:
While Nelson was waiting for news of the French, the British admiral Sir Robert Calder and his squadron met the Armada which tried to leave the Spanish waters. Sir Robert's ships captured two Spanish ships and forced the Armada to withdraw again to Ferrol. In England Nelson got the message that the Armada was still lying in Ferrol. The French tried to reach the coasts of England a second time. They wanted to reinforce themselves with the squadron of Rochefort, but the Armada and the squadron missed each other. Admiral Villenneuve set course on Cadiz, because he thought that Cadiz would be the better and safer port to wait for further messages from Napoleon. Nelson was informed by captains of the blockade fleet of Cadiz that the French would stay there longer. He travelled to Portsmouth and prepared his flagship, the famous Victory, for the coming decisive battle between the two European powers. On 15th of September, he left Portsmouth and arrived at Cadiz on the 28th. At the same time, the British Admiralty called Sir Robert Calder home to stand trial for his action. The British population was angry about him, because he hadn't destroyed the Armada. He had only forced it to return.

Lord Nelson understood him and gave him the 98 gun ship "Prince of Wales" for the return journey, because he could appreciate the situation Calder had been in, when he had met the Armada. Nelson paid honor to Calder with the 98 gun ship, because Nelson had also been able to give a small powerless frigate. The "Prince of Wales" with its 98 heavy guns would have been useful and efficient in the Battle of Trafalgar if it had been there.

In Cadiz:
In front of Cadiz Nelson had 27 ships of the line, some frigates and sloops under his command and waited for the French break out-movement. His second commander in chief was his old friend Cuthbert Collingwood. The third British flagofficier was Northesk on board of the "Britannia".

On the French side Napoleon was very dissatisfied with Vice-admiral Villenneuve, because his splendid plan to conquer England had failed. He gave up his plan of invading England and said, "Give me the control of the Channel for only one day and England will lie down at my feet!"

Napoleon ordered that Villenneuve would be replaced by a new Admiral who would come some days later. The new task of the Armada would be to sail in the Mediterranean Sea and support landing operations on the coast of Italy. Villenneuve didn't want to be replaced and so he broke out of Cadiz in a dark night, when the English under command of Lord Nelson let the Armada come out. Villenneuve was thinking that he had broken out so suddenly that the English hadn't been able to stop his movement, but Nelson let the French leave the port to defeat them in a battle off the Spanish coast.