A man and a woman digging a tunnel or shelter, to be used in case of an attack by the Soviet Union. In the background on the right a big sign board with a Mao slogan dating from 1969, when the Chinese-Russian relations were at its worst: 深挖洞、广积粮、不称霸 - Dig deep holes, store food and do not claim hegemony. Behind the sign anti-aircraft artillery can be seen.