Complex sentence: Tension developed between Cossiga and the President of the Council of Ministers Giulio Andreotti emerged when Andreotti revealed the existence of Gladio, a Stay-behind organization with the official aim of countering a possible Soviet invasion through sabotage and guerrilla warfare behind enemy lines.
Split into simpler sentences: Tension developed between Cossiga and the President of the Council of Ministers Giulio Andreotti. This tension emerged when Andreotti revealed the existence of Gladio, a Stay-behind organization with the official aim of countering a possible Soviet invasion through sabotage and guerrilla warfare behind enemy lines.