Why did Pius IX forbid Italian Catholics from taking part in politics in 1874?

In 1874, Pope Pius IX reaffirmed the non expedit ("it is not expedient"), a policy that prohibited Italian Catholics from participating in national political life as either candidates or voters.1

This directive was a direct response to the unification of Italy and the subsequent dissolution of the Papal States. When Italian forces captured Rome in 1870 and established it as the capital of the new Italian state, the papacy was deprived of its long-standing temporal lands.123

Pius IX refused to recognize the legitimacy of the new Italian government, which he viewed as having unjustly seized church territory. By forbidding Catholics from engaging in the political process, the Pope sought to protest this incorporation and withhold recognition of the state. This policy of political absenteeism was maintained by the Holy See for decades, effectively preventing the formation of a strong Catholic party in Italian national politics until the ban was formally lifted in 1919.1234