The main event in the First Republic in the sixties was the inclusion of the Socialist party in the government, after the reducing edge of the Christian Democracy (DC) had forced them to accept this alliance; attempts to incorporate the Italian Social Movement (MSI) in the Tambroni government led to riots, and were short-lived.

Aldo Moro, a relatively left-leaning Christian democrat, inspired this alliance. He would later try to include the Communist Party as well, with a deal called the historical compromise. This attempt at compromise was, however, stopped by the kidnapping and murder of Moro in 1978 by the Red Brigades, an extremist left-wing terrorist organization.

The Communist party was at this point the largest communist party in western Europe, and remained such for the rest of its existence. Their ability to attract members was largely due to their pragmatic stance, especially their rejection of extremism, and to their growing independence from Moscow (see Eurocommunism). The Italian communist party was especially strong in areas like Emilia Romagna, where communists had been elected to stable government positions. This practical political experience may have contributed to their taking a more pragmatic approach to politics.
[edit] The Years of Lead
See also: Strategy of tension

On 12 December 1969 a roughly decade-long period of extremist left- and right-wing political terrorism, known as the years of lead (as in the metal of bullets, Italian: anni di piombo), began with the Piazza Fontana bombing in the center of Milan. Neofascist Vincenzo Vinciguerra later declared the bombing to be an attempt to push the Italian state to declare a state of emergency, in order to lead to a more authoritative state. A bomb left in a bank killed about twenty, and was initially blamed on anarchist Giuseppe Pinelli. This accusation was hotly contested by left-wing circles, especially the Maoist Student Movement, which had support in those years from some students of Milan's universities, and who considered the bombing to have all the marks of a fascist operation. Their guess proved correct, but only after many years of difficult investigations.

The strategy of tension attempted to blame the left for bombings carried out by right-wing terrorists. Fascist "black terrorists," such as Ordine Nuovo and the Avanguardia Nazionale, were, in the 1980s-90s, found to be responsible for several terrorist attacks. On the other extreme of the political spectrum, the leftist Red Brigades carried out assassinations against specific persons, but weren't responsible for any blind bombings. The Red Brigades killed socialist journalist Walter Tobagi, and, in their most famous operation, kidnapped and assassinated Aldo Moro, president of the Christian Democracy, who was trying to involve the Communist Party in the government through the compromesso storico ("historic compromise"), to which the radical left, as well as Washington, were opposed. It is worth noting that the Red Brigades met fierce resistance from the Communist Party and the trade unions; some left-wing politicians, however, used the sympathetic expression "comrades who are mistaken" (Italian: Compagni che sbagliano) to refer to the Red Brigades. Some, including the prosecutor of Moro case Ferdinando Imposimato, have alleged that the 2nd Red Brigades (those led by Mario Moretti) were exploited - or anyway allowed to act freely - by Andreotti's government and possibly foreign forces (notably United States) to destabilize Italy, discredit the Communist Party and impede the historic compromise.

The last and largest of the bombings, known as the Bologna massacre, destroyed the city's railway station in 1980. This was found to be a neofascist bombing, in which Propaganda Due was involved.

On 24 October 1990 Prime minister Giulio Andreotti (DC) revealed to the Parliament the existence of Gladio, NATO's secret "stay-behind" networks which stocked weapons in order to facilitate an armed resistance in case of a communist coup. In 2000, a Parliament Commission report from the Olive Tree (centre-left) coalition concluded that the strategy of tension followed by Gladio had been supported by the United States to "stop the PCI and, to a certain degree, the PSI [Italian Socialist Party] from reaching executive power in the country."