the war of the third coalition was a european war during the years 1803 to 1806. during the war, france and the countries it conquered, led by napoleon i, defeated an alliance, called the third coalition. the third coalition was made up of the holy roman empire, russia, britain and others. the main fighting in central europe ended with napoleon's victory at the battle of austerlitz in 1805 but a smaller campaign continued in italy until napoleon won there, too.