Patrols, watchtowers and observation posts were always manned by two or three guards at a time. They were not allowed to go out of each other's sight in any circumstances. If a guard attempted to escape, his colleagues were under instructions to shoot him without hesitation or prior warning;[1] 2,500 did escape to the West, 5,500 more were caught and imprisoned for up to five years,[83] and a number were shot and killed or injured in the attempt.