A quick overview of the history of "the Papal States"
One can't understand the deal which the papacy made with the Fascist dictator, Benito Mussolini, without understanding the history of the relationship between the papacy and the civil governments of the Italian peninsula during the prior hundred years. After having had political control of "the Papal States", a good portion of central Italy, for a thousand years or more, the popes were denied that control during the 19th century.
[ excerpted from : http://www.historyworld.net/wrldhis/PlainTextHistories.asp?groupid=707&HistoryID=aa68>rack=pthc#ixzz0bOdqXaKY and http://ivarfjeld.wordpress.com/2009/06/16/ousted-pope-brought-back-by-the-fascists/ ]
First, the Papal States were taken away between 1797 and 1814 :
Between 1797 and 1809, a struggle between Pope Pius VI (1775-1799) and Napoleon, who emerged from the French Revolution as the emperor of France, resulted in the occupation of Rome by French troops, the removal of Pope Pius VI to France - where he died in 1799 - the annexation of all of the papal states into "the Napoleonic kingdom of Italy" and proclamation by Napoleon that the pope, Pius VII (1800-1823), no longer had any form of temporal authority. When Pius VII responded by excommunicating Napoleon himself and everyone else connected with this outrage, he was immediately arrested and removed to imprisonment in France. The entire Italian peninsula was under French control from 1809 to 1813 when Napoleon was defeated at Leipzig.
Then, the Papal States were returned between 1814 and 1869 :
The Papal states were returned to the Catholic Church by Catholic Austria and Pius VII returned to Rome in 1814 He and Popes Leo XII (1823-1829), Pius VIII (1829-1830) and Gregory XVI (1831-1846), and Pius IX (1846-1878) ruled over that territory for the next 65 years, except for a brief interlude when a short-lived Republic exiled Pius IX from Rome in 1848-49.
Finally, in 1871, the former Papal States were permanently taken away from the popes and absorbed into the modern nation of Italy :
Pope Pius IX convened the First Vatican Council in 1869, which decreed Papal infallibility. But that didn't make the pope invincible. On September 10 in 1870 Italy declared war on the Papal States. In October, Rome and the surrounding Campagna, voted for a union with the kingdom of Italy. Even the people who lived in Rome, voted against the Pope in a referendum. They wanted to be a part of the new Kingdom of Italy, with religious freedom, without a Pope as their religious head. Rome became once again, for the first time in thirteen centuries the capital city of a united Italy.
Pius IX ( 1846-1878 ) refused to accept these developments. He described himself as a prisoner in the Vatican. However the new Italian control of Rome did not wither, nor did the Catholic world come to the Pope's aid, as Pius IX had expected. In 1882, Pope Leo XIII ( 1878-1903) even considered moving the papacy to Trieste or Salzburg, two cities in Austria. However, he and his successors, popes Pius XII (1903-1914), Benedict XV (1914-1922) and Pius XII (1922-1939) continued to govern the Catholic Church from the 109 acre Vatican compound where they acted the part of victims hoping for someone to ride to their rescue, until 1929.
With this as the historical background, it's not surprising that the Catholic Church was willing to make a deal ("concordat") with Benito Mussolini, which became the model for its deal with Mussolini's partner, Adolf Hitler, four years later. As bad as these deals were, they were better - from the Vatican's point of view - than the hand that had been dealt to the church from the liberal revolutionaries of France and Italy, or what they could expect if the communists got their way in any additional Catholic countries.