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".