 Complete the following phrase:  During the Soviet-led invasion of Czechoslovakia in 1968, the Soviet Union used a series of white stripes on the armoured vehicles of its invasion forces because they used predomitly the same types of combat vehicles as the armed forces of Czechoslovakia both were Warsaw Pact allies. The markings consisted of one long white strip in the middle of the vehicle from the front and across the roof all the way to the back with two additional strips in the middle of both sides. This is similar to the markings applied on most Soviet tanks and armoured fighting vehicles 