The Lugou Bridge Incident was a battle between Japan's Imperial Army and China's National Revolutionary Army, marking the beginning of the Sino-Japanese War (1937-1945). The marble bridge itself (Lugouqiao) is a great work of eleven arches, restored by the Kangxi Emperor (1662-1722).
Japan had occupied Manchuria in 1931 and had created a nominally independent state of Manchukuo with Henry Puyi, the last monarch of the Qing Dynasty, as its sovereign. That state is widely regarded to have been a puppet government with real power concentrated in the hands of the Japanese, which constituted the only significant military forces in Manchuria. Although the Kuomintang and the international community refused to recognize the legality of the Japanese occupation, a truce had been negotiated in 1931.
At the end of 1932, the Japanese Guandong Army invaded Chahar Province. The Kuomintang's 29th Army, led by General Song Zheyuan and armed only with spears and obsolete rifles, resisted the attack, resulting in the War of Resistance at the Great Wall. The province fell to the Japanese after their predictable victory, therefore areas to the west of Beijing were under Japanese control.
In 1933, Japan annexed Rehe using the security of Manzhouguo as a pretext. Consequently all areas north of the Great Wall and hence north of Beijing fell to Japan. He Yinqin and Umezu Yoshijiro (1888-1949) signed an agreement on June 9, 1935, known as the He-Umezu Agreement recognizing Japanese occupation of Hebei and Chahar. Later that year, Japan established yet another puppet government, the East Ji Anti-Communist Autonomous Administration abbreviated as East Ji Autonomous Government. As a result, at the start of 1937 areas occupied by Japanese surrounded Beijing at north, west and east.
Japanese installations of various puppet governments were deliberate attempts to annex the whole of China by nibbling. The puppet government at Nanjing with Wang Jingwei as head was another obvious example.
Beginning late June 1937, the Japanese army (several hundreds) deployed at the west end of the bridge was practicing while Kuomintang forces, garrisoned in Wanping Town, watched closely. At dawn on 7 July, the Japanese army telegraphed the KMT forces saying that a soldier was missing and believed to be hiding inside the town. The Japanese demanded that its army should enter the town to search for the missing soldier, who was later found unharmed. There are some disputes among historians over the incident with some historians believing that this was an unintentional accident while others believing that the entire incident was fabricated by the Guandong Army in order to provide a pretext for the invasion of central China.
Colonel Ji denied the request backed by his superior, General Song. In the evening of 7 July, Matsui gave Ji an ultimatum that KMT troops must let Japanese troops enter the town within the next hour or the town would be fired upon. The Japanese artillery had already aimed at the town when the ultimatum was sent. At midnight 8 July, Japanese artillery units started bombarding the town while the infantry with tanks marched across the bridge at dawn. With orders from Song, Ji led the KMT forces of about 1000 to defend at all cost. The Japanese army partially overran the bridge and vicinity in the afternoon. KMT forces, after reinforcement from nearby units, outnumbered the Japanese and retook it completely next day. The Japanese army then halted the attack and offered to negotiate, marking the end of Phase I. Nevertheless the Japanese Army remained concentrated at the west end of the bridge.
During the meeting of all senior KMT officers of the 24th Army in Beijing on 12 July, Qin insisted that KMT forces must continue defending and resist any temptation to negotiate with the Japanese, whom he did not trust. Zhang in turn argued the incident on 7 July could still be settled by negotiation. Song then sent Zhang as KMT representative to Tianjin to meet General Hashimoto, the commander of all Japanese forces around the cities of Beijing and Tianjin and in Chahar and Rehe Provinces.
At the beginning Hashimoto told Zhang that the Japanese hoped the incident on 7 July could be settled peacefully. Zhang was encouraged by his friendly gesture and telegraphed Song that any more Kuomintang forces around Beijing would be viewed as an escalation and anger the Japanese. However Song thought Hashimoto was only buying time since he received various reconnaissance reports indicating increasing accumulation of Japanese forces from Manchuria and Korea around Beijing. As the recent Chinese victory relied on outnumbering the opponent, he transferred Zhao's 132nd Division accompanied by Qin to a station at Nanyuan Town which was between the bridge and Beijing to keep up the pressure from concentration of Japanese forces. Similar to most KMT and CPC (Communist Party of China) forces, the 29th Army was equipped with only rifles and just enough mortars and heavy machine guns, compared to better armed, trained and commanded Japanese troops whose tanks the Chinese armies still did not have any weapon capable of destroying.
With the fall of Beijing on 29 July and Tianjin on 30th, the North China Plain was helpless against Japanese mechanized divisions who occupied it by the end of the year. The Chinese armies (KMT and CPC) were on constant retreat until the hard fought Chinese victory at Tai er zhuang.