The Guandong army (関東軍) was a unit of the Japanese Army which along with the Central China Expeditionary Force conducted operations in Mainland China as part of the Sino-Japanese War (1937-1945).
Although the Army was nominal subordinate to the Japanese High Command, most historians believe that the Guandong Army was able to conduct its own operations without much control from above.
The Army was responsible for a number of war crimes and atrocities including biological warfare experiments on civilians conducted by Unit 731 and the Wan Bao Hill Incident.
See also: Battle of Nanjing, Battle of Lugou Bridge, Battle of Halhin Gol, History of Japan, History of China, World War II