The Battle of Trafalgar was important because it confirmed the superiority of the British Navy and smashed the strength of Napoleon's navy. The British victory utterly destroyed Napoleon's plan to invade Britain and secured the sea lanes for British maritime trade.
Ships led by British admiral Horatio Nelson joined a nearby British fleet in late September of 1805 in response to a fleet of French and Spanish ships sheltering near Cadiz, Spain. Nelson's arrival prompted the commander of the Franco-Spanish fleet, Admiral Pierre-Charles Villeneuve, to attack near Cape Trafalgar on Oct. 21.
Nelson ordered his fleet to respond using unorthodox techniques, bearing down on the allied ships with two columns led by the two largest vessels. This approach broke up the allied line, allowing the British ships to get in close proximity to the allied vessels. The superior British gunnery skills and tactical coherence led the British to a victory in which they captured more than 20 enemy ships and thousands of enemy sailors.
This victory crippled French maritime ambitions and secured the primacy of the British fleet for more than a century. However, it came at a cost. Admiral Nelson suffered an injury during the battle that led to his death.