In support of this plan, the French squadron based at Rochefort put to sea in July 1805, initially with the intention that they would join the Atlantic Fleet from Brest.

With the planned invasion impossible, Allemand began commerce raiding in the Eastern Atlantic, capturing 43 merchant ships during his cruise and successfully disrupting the British blockade of Cadiz.

Despite repeated orders issued to the Atlantic fleet instructing them to sail to Martinique, Vice-Admiral Honoré Ganteaume had failed in his one effort to break out of Brest during March and then given up.

[5] Allemand sailed from Rochefort on 16 July while the blockade squadron under Rear-Admiral Charles Stirling was out of position, rapidly escaping the coast into the Atlantic.

[11] Without instructions from his superior, and with no idea where the main French fleet was, Allemand spent much of August off the Spanish coast before deciding to turn to the third aspect of his orders, the disruption of British trade.

As a result, there were a number of independently sailing merchant ships in the Bay of Biscay and Allemand encountered and captured three on his journey north into the area later known as the Western Approaches.

[15] Armide was far more nimble than the lumbering Calcutta, and rapidly passed her out of range of her broadside, the frigate turning about and opening fire with her stern chasers, cannon mounted in the rear of the ship, at 15:00.

The two ships then opened a heavy fire on one another which continued for an hour until Armide, with her rigging badly damaged, drew back towards the rapidly approaching French squadron.

The larger and more powerful Magnanime inflicted severe damage to the British ship's rigging, rendering her unable to manoeuvre or escape, with the remainder of the French squadron bearing down.

In the aftermath of the engagement, it took two days to repair the battered Calcutta and in that time the convoy had safely passed Allemand's former position without sighting the French force.

There Allemand anchored for a time at the Spanish island of Tenerife, where he was able to repair and resupply his squadron before embarking on a lengthy cruise against the British convoys that regularly crossed the region.

[17] The British fleet did not lose a single ship, but the cost of the victory was severe: Lord Nelson, victor of four major battles in the previous eight years, had been killed at the height of the combat by a musket ball.

However, the four ships of the French vanguard, which had rapidly outdistanced the battle and not returned, escaped towards the Bay of Biscay under Contre-Admiral Pierre Dumanoir le Pelley.

Unaware of the events of Trafalgar and assuming these ships to be a part of Allemand's force, Captain Dundas sought to lure them towards Strachan's squadron, which he knew to be in the area.

[19] As these events unfolded Allemand was many hundreds of miles to the south, preying successfully on the trade that passed along the African coast without any serious opposition from major British forces, which were still largely confined to European waters.

[20] On 20 November, with his supplies running low, Allemand attacked a convoy of seven ships sailing from Britain to Gorée, passing close to the Savage Islands.

[21] Although his attack was successful, Allemand was unable to prevent the escape of the convoy's escort, the 18 gun brig HMS Lark under Commander Frederick Langford.

Making all sail northwards in search of reinforcements, Langford encountered his target on 26 November, meeting HMS Agamemnon, one of the ships that made up the squadron under Vice-Admiral Sir John Thomas Duckworth.

Duckworth had, with his subordinate Rear-Admiral Thomas Louis, been ordered to keep a close blockade on Cadiz in case the remainder of the combined fleet that still sat at anchor there should try to escape.

Duckworth continued southwards for much of December 1805, only turning back north once he had reached the Cape Verde Islands, a point far too far south for Allemand to have been operating in.

Accepting that his enemy had escaped him, Duckworth turned back north but soon afterwards ran into the frigate HMS Arethusa under Captain Charles Brisbane, whose large convoy had been broken up by an unidentified French battle squadron in the Bay of Biscay.

[25] The French naval authorities considered Allemand's cruise a major success in a year that had cost them huge numbers of ships and men.

For minimal casualties, Allemand had inflicted a blow against British Atlantic trade and tied up substantial Royal Navy resources during a complicated and strategically vital campaign.