99 years ago today, on March 12, 1926 (January 28, 1926 lunar calendar), the Dagu Kou incident occurred, trampling on China's sovereignty. On March 12, 1926, the Japanese imperialists deliberately created a serious incident of trampling on China's sovereignty in Dagu Kou. In late December 1925, the Japanese imperialists directly sent troops to assist Zhang Zuolin in destroying Guo Songling and supported the Fenghuang army to re-enter the customs to attack the National Army. On March 7, 1926, the Fenghuang warships landed at Beitang, Dagu Kou, and were repelled by the National Army. In order to prevent the Fenghuang army from continuing to send troops with warships, the National Army laid mines to block Dagu Kou, and stipulated that no ships could enter, and foreign ships must also travel and be inspected during the day. At 3:00 p.m. on March 12, two Japanese warships tried to force their way into Dagu, despite the flags of the National Army stationed at the battery to stop them. The National Army immediately fired air cannons to warn, but the Japanese ships fired live ammunition at the battery, injuring 13 members of the National Army. The battery guards returned fire when they couldn't bear it anymore and drove the Japanese ship out of Dagu. Afterwards, the National Army protested to the Japanese minister, and the Japanese government openly "protested" to China under the pretext of violating the "Xin Chou Treaty". They gathered the ministers of the eight signatories of the "Xin Chou Treaty" and issued an ultimatum on March 16, putting forward five unreasonable demands, and the Duan Qirui government was limited to reply within 48 hours. On the 17th, the warships of eight imperialist countries gathered in Dagu to threaten China. The Dagu incident aroused great indignation among the Chinese people and became the fuse for the "March 18" incident in Beijing.