It was initially composed of a regular army division and a heavy siege artillery batallion, both stationed within the Kwantung Leased Territory. Supplementing this force were a six independent garrison battalions of the railway guards deployed along the railway zone, making a total troop strength of 10,000 men. Since the reorganization in 1919, the military unit was called the Guandong Army.
Although the Army was nominally subordinate to the Japanese High Command, conspirators of the Army plotted the assassination of Zhang Zuolin in 1928 and the Manchurian Incident (1931) leading to the foundation of Manchuguo in 1932. The Guandong Army was largely augmented, up to 700,000 in 1941, to defend the whole territory of Manchuria. Generals and young officers virtually controlled the puppet government of Emperor Henry Pu Yi.
The Army fought against the Red Army of the Soviet Union at Zhanggufeng in 1938 and Nomonhan in 1939. Since the outbreak of the Pacific War, many troops were mobilized to the Pacific islands from Manchuria. When the Soviet Red Army invaded Manchuria in August 1945, the Army retained approximately 600,000 soldiers. To cope with the Soviet invasion, the Army planned to form the defence line near the capital of Manchuguo, but the Emperor of Japan Hirohito ordered them to surrender before the main defensive engagement took place.
See also: History of Japan, History of China, World War II
Although the Kantogun was nominally subordinate to the Japanese High Command, its leadership demonstrated significant self-determination, as conspirators in the Army plotted the assassination of Zhang Zuolin in 1928 and the Manchurian Incident (1931) leading to the foundation of Manchuguo in 1932.
The Army fought against the Soviet Union's Red Army at Zhanggufeng in 1938 and Nomonhan in 1939, sustaining heavy casualties.
During Operation August Storm, the Soviet Red Army's invasion Japanese-occupied Manchuria in August 1945, the Kantogun's strength was nearly 600,000.
The Japanese GuandongArmy at the region was a combination of infantry, tanks, mechanized forces, artillery and cavalry.
The 3rd (2nd?) Division of the GuandongArmy from Chahar Province and the 15th (9th?) Division from Manchuria and troops from Phase I were all commanded by General Hashimoto (橋本大將).
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.