Japanese troops attack Yan'an with air strikes on October 15, 1939. Many munitions depots caught fire and the whole city was covered by thick black smoke. [Photo: Xinhua]

Pictures of Japanese air stricks on Yan'an during Chinese People's War of Resistance against Japanese Aggression were released on Tuesday by the Beibei District Archives in southwest China's Chongqing.

The documents include first-hand accounts provided by military personnel, which can better help readers understand the real situation in the combat zones of Yan'an during that time.

All the documents provided by Beibei District Archives are collected from non-governmental organizations and individuals.