The Ranzhuang tunnel evolved in the course of resisting Japanese's mopping-up operations in the central Chinese Hebei province. During the Second Sino-Japanese war, the Chinese Communist forces or local peasant resistance used tunnel war tactics against the Japanese (and later Kuomintang during Chinese Civil War). The tunnels were dug beneath the earth to cover the battlefield with numerous hidden gun holes to make a surprise attack. Entrances usually were hidden beneath a straw mat inside a house, or down a well. This allowed flexible manoeuver or exit.