The Battle of Trafalgar took place October 21, 1805. In the months leading up the battle, the English navy blockaded the French in Cadiz, Spain to prevent the French navy from receiving supplies and to stop the fleet from assisting Napoleon, who was planning an invasion of England. French Vice-Admiral Villeneuve disobeyed orders to head north to France from fear of an English attack, so Napoleon abandoned plans to invade England and, instead, headed east to battle the Austrians and Russians, now giving the order to the French navy to go to Naples to assist the French army. At Villeneuve's hesistation, Napoleon appointed Vice-Admiral Rosily to replace Villeneuve, who learned of Napoleon's plan and decided to sail east through the Strait of Gibraltar to avoid being disgraced.
Source: Nelson's Trafalgar by Roy Adkins
The paintings above are Battle of Trafalgar by George Chambers (1803-1840) and Captain Horatio Nelson (1781) by John Francis Rigaud.