On December 12, 1969, a bomb exploded in the Piazza Fontana in the center of Milan. This act of terror initiated ten years of political terrorism in Italy, between left and right wing extremists. The term 'Years of Lead' is translated from the Italian, 'Anni di Piombo', refering to lead used to make bullets.
The Milan bomb was left in a bank and killed about twenty people. It was originally blamed on anarchist Giuseppe Pinelli. This accusation was hotly contested by left-wing circles, especially the Maoist Student Movement which was popular among the students of Milan's universities, and who considered the bombing to have the hallmark of a fascist operation.
Their guess eventually proved correct, but only after many years of difficult investigations. 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.
Italy's left-wing organisations continued to be blamed 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 individuals, 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 include 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', ('Compagni che sbagliano', in Italian) to refer to the Red Brigades. Some radical left apologists have alleged that the Red Brigades (or at least the 2nd Red Brigades, led by Mario Moretti) were exploited by the right-wing or even possibly by foreign forces to destabilise Italy, discredit the Communist Party and impede the historic compromise. This is a hotly contested claim that the evidence does not support and which many consider to have the hallmarks of a 'Blame-the-Victim' conspiracy theory.