The 1823 papal conclave was convoked following the death of Pope Pius VII on 20 August 1823. The conclave began on 2 September and ended 26 days later with the election of Cardinal Annibale Sermattei della Genga who became Pope Leo XII. Pius VII, who had been elected in 1800, had reigned as Pope for what was considered a very long pontificate. During his reign as Pope, the Catholic Church had faced, in the French Revolution and its aftermath, a severe attack on its power and legitimacy. Pius himself had been a prisoner of Napoleon in France for six years.