On June 6, 1941, Japanese planes carried out fatigue bombing of Chongqing. More than 5,5 people suffocated in air defense tunnel. City will hold a city-wide air defense siren test on 5 June every year to commemorate the victims of the bombing. "The pain in our hearts can never be erased," survivor Su Yuankui said. 'The shadow and after-effects of the 'Chongqing bombing' have stayed with me for the rest of my life,' survivor Chen Guifang said.