The Congress of Vienna and subsequent Congresses constituted a major turning point – the first genuine attempt to forge an 'international order', to bring long-term peace to a troubled Europe, and to control the pace of political change through international supervision and intervention.
The Congress of Vienna lasted for 40 years, it was signed on June 9, 1815, by the “eight” (except Spain, which refused as a protest against the Italian settlement). All the other powers subsequently acceded to it. As a result, the political boundaries laid down by the Congress of Vienna lasted, except for one or two changes, for more than 40 years.
Subsequently, Ferdinand IV, the Bourbon King of Sicily, regained control of the Kingdom of Naples after Joachim Murat, the king installed by Bonaparte, supported Napoleon in the Hundred Days and started the 1815 Neapolitan War by attacking Austria.