[1] Leo XII was in ill health from the time of his election to the papacy to his death less than 6 years later, though he was noted for enduring pain well.

During the dozen or more years he spent in Germany he was entrusted with several honourable and difficult missions, which brought him into contact with the courts of Dresden, Vienna, Munich and Stuttgart, as well as with Napoleon.

[5] After the Napoleonic abolition of the States of the Church (1798), he lived for some years at Monticelli Abbey, solacing himself with music and with bird-shooting, pastimes which he continued even after his election as Pope.

In the conclave of 1823, della Genga was the candidate of the zelanti faction and in spite of the active opposition of France, he was elected as the new pope by the cardinals on 28 September 1823, taking the name of Leo XII.

[6] It was said in the conclave that he lifted his robes to show the cardinals a pair of swollen and ulcerated legs to deter them, but that made them even more eager to elect him.

[10] Leo XII's foreign policy, entrusted at first to the octogenarian Giulio Maria della Somaglia and then to the more able Tommaso Bernetti, negotiated certain concordats very advantageous to the papacy.

Personally most frugal, Leo XII reduced taxes, made justice less costly, and was able to find money for certain public improvements, yet he left the Church's finances more confused than he had found them, and even the elaborate jubilee of 1825 did not really mend financial matters.

[5] Leo XII's domestic policy was one of extreme conservatism: "He was determined to change the condition of society, bringing it back to the utmost of his power to the old usages and ordinances, which he deemed to be admirable; and he pursued that object with never flagging zeal.

[12][13] "The results of his method of governing his states soon showed themselves in insurrections, conspiracies, assassinations and rebellion, especially in Umbria, the Marches and Romagna; the violent repression of which, by a system of espionage, secret denunciation, and wholesale application of the gibbet and the galleys, left behind it to those who were to come afterwards a very terrible, rankling and long-enduring debt of party hatreds, of political and social demoralisation, and – worst of all – a contempt for and enmity to the law, as such.

Leo XII made himself unpopular with the people due to the fact that he constrained them to endless rules that concerned private life and public affairs.

[7] While often considered an archconservative Leo XII held a high opinion of the liberal Catholic priest Lamennais having a portrait of him hung in his private chambers.

According to Cardinal Nicholas Wiseman before the full consistory he said that Lamennais was " a distinguished writer, whose works had not only rendered eminent services to religion, but rejoiced and astonished Europe."

Champollion later wrote to Cardinal Wiseman that "It is a real service which his Holiness renders to science, and I shall be happy if you will be good enough to place at his feet the homage of my profound acknowledgment.

Donald J. Keefe in his paper "Tracking the footnote"[18] traced a quote by Leo XII which strongly condemned vaccination to "an unverified citation" by Dr. Pierre Simon in Histoire et philosophie du contrôle des naissances.

The authors credit the origin of the mythical vaccination ban of Leo XII to the personality of Cardinal della Genga when he became pope in 1823.

He also beatified Yolanda of Poland and Maddalena Panattieri on 26 September 1827 as well as Giovanna Soderini (1827) and Elena Duglioli and Juana de Aza (the mother of Saint Dominic) in 1828.

For the December 1824 allocations, Leo XII considered elevating Félicité de La Mennais despite knowing about his crude character and extreme social and moral positions.

The minister to Rome for French King Charles X, François-René de Chateaubriand, who was near to the events, wrote: "The pope died of that haemorrhoidal condition to which he was subject.

Leo XII is considered to have been a man of noble character, with a passion for order and efficiency, but one who lacked insight into the temporal developments of his time.

His rule was unpopular in Rome and in the Papal States, and by various measures of his reign he diminished greatly for his successors their chances of solving the new problems that confronted them.