The War of the Third Coalition aligned Britain, Russia, Austria and other European powers against a French-led group that included Spain and several dependent or allied states. France's political system also shifted during the war, becoming the First French Empire in 1804. The invasion threat existed in two forms: a general fear that France might attack and the immediate danger created when a fleet and troops were ready to move. For most of the war, Britain faced the first condition. Trafalgar's strategic value lay in preventing the second by denying France a plausible maritime route across the Channel.
Chapter · 3:00-5:45
The Third Coalition and the threat of invasion
The campaign is placed in the wider War of the Third Coalition, where an invasion of Britain was feared but not yet an imminent landing.