Monument introduction: Hailar Fortress is based on Aobao Mountain and Beishan position-style military fortifications. It is composed of two parts connected above ground and underground. The underground fortifications are 12 to 17 meters away from the ground. It is built using underground excavation method. Each resistance hub has several fire support points. Build many permanent steel plate concrete firepower points, command posts and observation posts, as well as howitzer, mountain artillery, infantry artillery and mortar launching positions, as well as reinforced concrete shelters, reinforced concrete roof fortifications and bunker groups. Fire support points are mostly built on high ground and combined with on-site obstacles to form a ring defense. The firepower points on each high ground are arranged in multiple layers to support each other with firepower. Each resistance hub and support point has several iron wire barriers, and some areas are also laid with mines. Construct several trenches and open-air gun seats around the permanent firepower points and main defense fortifications, which can not only supplement the firepower distribution of the permanent fortifications, but also support and defend the permanent fortifications from attacks and blockades. Most of the permanent firepower points are connected to underground fortifications by secret passages. The headquarters of the Japanese Kwantung Army paid special attention to the defense of tanks in the construction of fortifications, building a large number of anti-tank obstacles, as well as anti-tank trenches more than 10 meters wide and more than 4 meters deep. Each resistance hub is connected by above-ground and underground telephone lines, and has a strong communication and command system.