The official name reflects Hamburg's history as a member of the medieval Hanseatic League and a free imperial city of the Holy Roman Empire. Before the 1871 Unification of Germany, it was a fully sovereign city state, and before 1919 formed a civic republic headed constitutionally by a class of hereditary grand burghers or . Beset by disasters such as the Great Fire of Hamburg, North Sea flood of 1962 and military conflicts including World War II bombing raids, the city has managed to recover and emerge wealthier after each catastrophe.