From 1963 to 1974, security intelligence services dealt with a series of domestic and foreign political events. At home, there were political confrontation both before and after the Brioni Plenum (1966), liberal flareups and massive leftist student demonstrations in Belgrade in 1968, "Hrvatsko proljeće" (Croatian Spring) or "MASPOK" (mass movement) in Croatia in 1971, a nationalist incursion of the Bugojno group in the Raduša area (1972), and a revival of nationalism in Yugoslav republics. The most significant event abroad was the invasion of the Warsaw Pact troops into Czechoslovakia in 1968.