20–21 September 1968 – The armies of the five countries of the Warsaw Pact (including the Polish forces) enter the territory of Czechoslovakia in order to stop the liberal political reforms of the Prague Spring. This intervention, codenamed “Danube”, is considered the largest military operation in post-war Europe. Colonel Ryszard Kukliński was one of the officers involved in its planning.
14–22 December 1970 – The so-called “December Events”: Workers in the coastal cities protest against the announced rises in the meat prices. They organize demonstrations, protests and strikes. Street riots break out and are brutally put down by the communist militia and army. Over ten thousand protesters are confronted by almost thirty thousand soldiers, supported by hundreds of tanks and APCs. Colonel Kukliński cannot believe that Polish soldiers are shooting at their countrymen.
11 August 1972 – Colonel Kukliński sends a letter from the German port of Wilhelmshaven to the US Embassy in Bonn. Writing in broken English, he asks for a meeting with a US army officer in Amsterdam. This is the beginning of his cooperation with the Americans. The impulse to establish contact with them was to a large extent triggered by the events in Czechoslovakia and on the Baltic coast.