Andreotti would create a new government consisting of Christian Democrats, Socialists, Social Democrats, and Liberals. In 1990, Andreotti revealed the existence of the Operation Gladio; Gladio was the codename for a clandestine North Atlantic Treaty Organization (NATO) "stay-behind" operation in Italy during the Cold War. Its purpose was to prepare for and implement armed resistance in the event of a Warsaw Pact invasion and conquest. Although Gladio specifically refers to the Italian branch of the NATO stay-behind organizations, "Operation Gladio" is used as an informal name for all of them. During his premiership, Andreotti clashed many times with President of the Republic Francesco Cossiga. European Union negotiations In 1990, Andreotti was involved in getting all parties to agree to a binding timetable for the Maastricht Treaty. The deep Economic and Monetary Union of the European Union favoured by Italy was opposed by Britain's Margaret Thatcher, who wanted a system of competition between currencies. Germany had doubts about committing to the project without requiring economic reforms from Italy, which was seen as having various imbalances. As President of the European Council, Andreotti co-opted Germany by making admittance to the single market automatic once the criteria had been met and committing to a rigorous overhaul of Italian public finances. Critics later questioned Andreotti's understanding of the obligation or whether he had ever intended to fulfil it. Resignation and decline In 1992, at the end of the legislature, Andreotti resigned from premiership; he was the last Christian Democratic Prime Minister of Italy. The previous year, Cossiga had appointed him Senator for Life. Andreotti was one of the most likely candidates to succeed Cossiga as President of the Republic in the 1992 presidential election. Andreotti and the members of his corrente had adopted a strategy of launching his candidature only after effectively quenching all the others. Allegations against him thwarted the strategy; moreover, the election was influenced by the murder of the anti-mafia magistrate Giovanni Falcone in Palermo. Later political life Tangentopoli In 1992, an investigation was started in Milan, dubbed Mani pulite. It uncovered endemic corruption practices at the highest levels, causing many spectacular (and sometimes controversial) arrests and resignations. After the disappointing result in the 1992 general election (29.7%) and two years of mounting scandals (which included several Mafia investigations which notably touched Andreotti), the Christian Democracy party was disbanded in 1994. In the 1990s, most of the politicians prosecuted were acquitted