The battle of Copenhagen started when Tsar Paul formed the League of Armed Neutrality with Prussia, Sweden, and Denmark, to enforce free trade with France against the British blockade. The British decided to attack Denmark to break up the league. The British needed to act before the Baltic Sea thawed and released the Russian fleet. If the Russian fleet joined with the Swedish and Danish fleets, the combined fleets would form a formidable force of up to 123 ships of the line.
Copenhagen is often considered to be Nelson's hardest-fought victory, ranked among battles such as the Battle of Trafalgar, as the Danes offered a very stubborn resistance.
What if the Danes managed to repel the British attack?