The Marco Polo Bridge Incident was a battle between the National Revolutionary Army of China and the Imperial Japanese Army that took place on July 7th, 1937. This conflict is commonly regarded as the beginning of the Second Sino-Japanese War and the resulting full-scale invasion of China by Japan.
The high-command in Japan's military did not want to be provoked into an escalation of its conflict with the Chinese, and following the incident at the Marco Polo Bridge it issued a formula for continued peace in China: withdrawal of Chinese troops from around the area of the Marco Polo bridge and from the left bank of the Yangtze River; guarantees that incidents such as had occurred at the Marco Polo Bridge would not happen again; punishment of those responsible for the incident; and an apology.
Contrary to the strategy of the high command, a faction within the Japanese army urged using the Marco Polo incident as an opportunity to send more troops to China. Konoe and his cabinet supported this recommendation, and the army high command went along with it so long as non-escalation of the conflict in China was observed.
The day after the incident at the Marco Polo Bridge, the CPC Central Committee issued a manifesto that called upon: "the people of the whole country, the government and the armed forces to unite and build the national united front as a Great Wall of resistance to Japanese aggression." It called upon the Kuomintang and the Communist party to "cooperate closely and resist the new attacks of the Japanese aggressors." On August 22 the Military Council of the National Government issued an order redesignating the Red Army as the Eighth Route Army of the National Revolutionary Army. And on September 22 the KMT Central News Agency published the "Announcement of Kuomingtang-Communist Cooperation by the Central Committee of the Communist Party of China," and the next day Chiang Kai-shek made a statement recognizing the legality of the Communist Party.
At this point, the incident might well be considered as having been settled, if the Japanese had conformed to the terms of the truce. But, it was later ascertained that some one hundred Japanese soldiers along the railway tunnel were not withdrawn as agreed. During midnight on 9 July 1937, the Japanese troops there again fired into the city. Thereafter, Japanese troops continued to pour into the troubled area. By 12 July, there were 20,000 Japanese troops and 100 airplanes in the area.
The Japanese promised not to invade Beijing and Tianjin upon agreement of all following terms:
1) The KMT must wipe out all anti-Japanese organizations and halt all anti-Japanese activities inside the cities.
2) The KMT must take all responsibilities of the incident on July 7.
3) Song, not any other inferior officer of the 29th Army, must apologize.
[General Zhang Zhizong] accepted the first term and the commander of the battalion under Colonel Ji Xingwen's command was to be relieved as an agreement to the second. However Zhang told Hashimoto that he could not decide on behalf of [General Song Zheyuan], thus could not agree on the third term at the time.
While this investigating body was being organized, Japanese troops forcibly tried to breach the Wanping defenses and were readily repulsed. Directly after this second skirmish, both sides rushed a battalion of men to the scene and, by the morning of July 8, a tense situation had arisen.
After the maneuvers, one Japanese soldier was found missing, and a request to search the area was made by Japanese troops. The Chinese unit, led by General Sung Che-yuan, also joined the search.
Chinese troops, startled by an unannounced action from their Japanese counterparts, began firing across the river in defense at about 11:00pm. Fire was briefly returned, then the incident seemed to have settled down just as quickly as it popped up...
In June of 1937, Japanese troops carried out military training near the western edge of the Marco Polo Bridge. The Chinese government requested advance notice be given so that the local people would not be alarmed. However, on July 7, 1937, the Japanese carried out nighttime training without any prior notice which alarmed the local Chinese forces.
Under the terms of the Boxer Protocol of 7 September 1901, China had granted nations with legations in Beijing the right to station guards at twelve specific points along railways connecting Beijing with Tianjin... Come July 1937, Japan had expanded to maintain forces estimated between 7000-15,000 men, mostly along the railways...
Marco Polo Bridge, located outside of the walled town of Wanping to the southwest of Beijing was the choke point of the Pinghan Railway (Beijing-Wuhan), and guarded the only passage linking Beijing to Kuomintang-controlled areas in the south. Prior to July 1937, the Japanese military had repeatedly demanded the withdrawal of all Chinese forces stationed in this area, and had attempted to purchase nearby land to build an airfield. The Chinese refused, as Japanese control of the bridge and Wanping town would completely isolate Beijing from the Kuomintang-controlled south.
Today, the bridge is known as the Lugouqiao which means "the moon over the Luguo Bridge at dawn." The bridge was originally built in 1192 but was destroyed in a flood and rebuilt sometime in the late seventeenth or early eighteenth century. The bridge is famous for its unique architecture containing eleven arches, 485 different stone lions, elephants that guard each end of the bridge, and two large stone steles which depict the rebuilding of the bridge and the famous Qing Dynasty.