A major milestone on the march to World War Two in the Pacific, the Manchurian Incident, also called the Mukden Incident, of 18-19 September 1931 expanded into the beginnings of fighting between Japan and China. 
It was planned by Lieutenant Colonel Kanji Ishiwara and Colonel Seishiro Itagaki, who were on the staff of the Kwangtung Army. Ishiwara, the theoretician, subscribed to a "Final World War Theory" that would determine if Japan or the United States would dominate the world. "In January 1928, at a meeting of the Mokuyo-kai (Thursday Society) group of elite officers who graduated from the Imperial Japanese Army's War College, Ishihara said, 'The nation could stand being in a state of war for even 20 years or 30 years if we have footholds all over China and fully use them.'" 
Japan controlled the Kwangtung Leasehold, a small area in Manchuria, containing Port Arthur and Darien. The South Manchurian Railroad Line, owned by a Japanese corporation, terminated in the Leasehold; the railroad provided cover for Japanese intelligence and covert action throughout Manchuria.
During July, the Kwangtung Army emplaced artillery along the line, and, on the 25th, two 9.5" Russian cannons hidden in a shed. One was aimed at the Mukden constabulary barracks, and the other of Chang Hsueh-liang's airfield. Itagaki testified to the IMTFE that
it is said that the disposition of the Chinese troops had recently been changed so that the japanese troops, widely dispersed in groups along the railway line, faced concentrations which threatened their annihilation; it is said that the behaviour of the Chinese troops towards the Japanese troops was provocative and insulting; it is said that all indications pointed to an unprovoked attack by the Chinese troops upon the Japanese troops, in which the latter would be overwhelmed, unless decisive counter-action was promptly taken. Therefore, it is said, a plan was drawn up whereby, if the Chinese attacked, the Kwantung Army would concentrate its main forces in the vicinity of Mukden and deliver a heavy blow to the nucleus of the Chinese forces in the vicinity of Mukden, and thus by sealing the fate of the enemy, would settle the matter within a short period. It was a part of this plan that two heavy guns should be secretly set up in the Mukden Independent Garrison Barracks. 
The Tribunal differed, however.
The Chinese troops had no plan to attack the Japanese. They were caught unprepared. In the attack on the Barracks, where there were thousands of Chinese troops, the Japanese fired form the darkness upon the brightly lit Barracks and met with trifling resistance, mainly from some Chinese troops who were cut off in their attempt to escape. In their capture of the city of Mukden, they met only negligible resistance on the part of some police."
At an August conference of field commanders at the Summer palace, Lieutenant General Shigeru Honjo, the new commander of the Kwangtung Army, was briefed, along with Suzuki and Itagaki, on clandestine communication with the Palace. War Minister Jiro Minami was not aware of the planning, and the generals were advised not to tell him too much, since he would be the intermediary between the Palace and the Cabinet.
On the night of 18 September 1931, Lieutenant Suemori Kawamoto and a detail from the Kwangtung Army triggered an explosion along the South Manchurian Railway Line, at Liu'tiaokou, north of Mukden, Manchuria. Kawamoto actually had intended to derail a train, but there was no actual damage to the Japanese-controlled tracks. Kawamoto then fired at the barracks, and the hidden howitzers began to shell them. Chang, however, was in Beijing at the time. When told of the attack, he directed his troops not to resist. 
Col. Seishiro commanded the 29th Infantry Regiment and Independent Garrison Force to attack the barracks, in Mukden, of the Chinese Manchurian Army. By 4 AM, they were in Japanese hands. Ishihara then gave a false report to overall Kwangtung Army commander Shigeru Honjo.
Using plans previously written by Ishiwara, Honjo ordered Japanese troops to move beyond the borders of the leased Japanese territory, and take control of towns along the railroad. They then began a campaign to seize major cities of Manchuria. Reports first reached the Palace from newspapers, in which the Kwangtung Army blamed the Chinese. Takeji Nara, Chief Aide-de-Camp to the Emperor, told Hirohito that he did not think the incident would spread, but that the Emperor should hold a conference to review the situation and take control. Other Imperial advisers, Nobuaki Makino and Kinmochi Saionji, overruled Nara, arguing that any failure of decisions made at such a meeting would "soil...the virtue of his majesty."
- Chapter V, Japanese Aggression Against China. Section I. Invasion & Occupation of Manchuria. The China War and Its Phases, International Military Tribunal for the Far East, pp. 544-564
- War Responsibility--delving into the past (1) / Who should bear the most blame for the Showa War?, Yomiuri Shimbun
- David Bergamini (1971), Japan's Imperial Conspiracy, Morrow, p. 1091
- Bergamini, pp. 416-417
- IMTFE Volume 5, p. 554
- IMTFE Volume 5, p. 556
- Bergamini, pp. 418-419
- Merion and Susie Harris (1991), Soldiers of the Sun: the Rise and Fall of the Imperial Japanese Army, Random House, pp. 152-153
- Herbert P. Bix (2001), Hirohito and the making of modern Japan, Harper Perennial, ISBN 978-0060931308, pp. 235-236