Since the Japanese invasion of Manchuria in 1931, there had been many small incidents along the rail line connecting Beijing with the port of Tianjin, but all had subsided.

[15]: 25  After the invasion, Japanese forces extended their control further into northern China, seeking to obtain raw materials and industrial capacity.

The significance of the Marco Polo Bridge incident is that, following it, tensions did not subside again; instead, there was an escalation, with larger forces committed by both sides and fighting spreading to other parts of China.

This number of men, and the amount of concomitant matériel, was several times the size of the detachments deployed by the European powers, and greatly in excess of the limits set by the Boxer Protocol.

When a Japanese soldier, Private Shimura Kikujiro, failed to return to his post, Chinese regimental commander Ji Xingwen (219th Regiment, 37th Division, 29th Army) received a message from the Japanese demanding permission to enter Wanping to search for the missing soldier; the Chinese refused.

Private Shimura later returned to his unit; he claimed to have sought immediate relief in the darkness from a stomach ache and become lost[19][citation needed]); according to Peter Harmsen, he had visited a brothel.

[citation needed] At 02:00 on 8 July, Qin Dechun, executive officer and acting commander of the Chinese 29th Route Army, sent Wang Lengzhai, mayor of Wanping, alone to the Japanese camp to conduct negotiations.

A verbal agreement with Chinese General Qin was reached, whereby:[citation needed] This was agreed upon, though Japanese Garrison Infantry Brigade commander General Masakazu Kawabe initially rejected the truce and, against his superiors' orders, continued to shell Wanping for the next three hours, until prevailed upon to cease and to move his forces to the northeast.

[citation needed] Although a ceasefire had been declared, further efforts to de-escalate the conflict failed, largely due to actions by the Chinese Communists and the Japanese China Garrison Army commanders.

[citation needed] Due to constant Chinese attacks, Japanese Garrison Infantry Brigade commander General Masakazu Kawabe ordered Wanping to be shelled on 9 July.

The Chinese 219th regiment staged an effective resistance, and full scale fighting commenced at Langfang on 25 July.

[citation needed] After launching a bitter and bloody attack on the Japanese lines on the 27 July, General Song Zheyuan was defeated and forced to retreat behind the Yongding River by the next day.

The Japanese gave Song and his troops "free passage" before moving in to pacify resistance in areas surrounding Beijing and Tianjin.

On 9 August 1937, a Japanese naval officer was shot in Shanghai, escalating the skirmishes and battles into full scale warfare.

[25] According to Jim Huffman this notion has been "widely rejected" by historians, as the Japanese would likely have been more concerned over the threat posed by the Soviets.