Less than half a year after the incident， Japanese forces occupied a territory of over 1 million square kilometers in the northeast. With Honjo"s approval， Itagaki and Ishiwara drafted the plan to fundamentally solve the Manchuria and Inner Mongolia issue and put it into practice. Upon Itagaki"s suggestion， Doihara instigated a riot in Tianjin on November 8， and two days later abducted Aisin Gioro Puyi to northeast China secretly. On February 16， 1932， Itagaki and Doihara incited a group of traitors to hold a meeting in Shenyang to "establish a state." In the name of the "Manchurian government，" Japanese aggressors declared on March 1 the founding of the puppet Manchukuo， with Changchun as its "capital." On March 9， Puyi assumed the office of "chief executive，" and in 1934 became the "emperor of Manchukuo."
On August 8， 1932， Itagaki was promoted major general， and appointed advisor to Manchukuo"s "chief executive." In February 1933， he acted as head of the secret service in Fengtian， set up an espionage agency in Tianjin， and plotted for the invasion of Rehe Province. On August 1， 1934， he served as supreme advisor to Manchukuo"s "civil and military ministry." On December 10 he was appointed Vice Chief of Staff of the Kwantung Army， while holding a concurrent post of military attaché to Manchukuo. On March 23， 1936， he was promoted Chief of Staff of the Kwantung Army， and on April 28 to lieutenant general.
"Valiant general" of the Japanese army
On March 1， 1937， Itagaki was appointed General Officer commanding the 5th Division. On July 7， Japanese forces provoked the Lugouqiao Incident and started an all-out invasion of China. Itagaki led the 5th Division to set off from Hiroshima， and landed in Tianjin in August by way of Pusan. Immediately they launched an offensive against the area along the Peiping-Guisui Railway. In the beginning of September， the 5th Division invaded Chahar and pushed forward to Shanxi Province. On September 25， the 21st Brigade of the 5th Division fell into an ambush at Pingxingguan by the Eighth Route Army， losing over 1，000. In October Itagaki led the 5th Division to join in the Xinkou and Taiyuan battles. Taiyuan fell on November 9. In the spring of 1938， Itagaki led the 5th Division again to join in the Xuzhou Battle. His troops suffered heavy casualties in the Battle of Taierzhuang.
On May 25 Itagaki was recalled to Tokyo to work in the General Staff. On June 3 he was appointed War Minister of Fumimaro Konoye"s Cabinet. From January 5 to August 30， 1939， he acted as War Minister of Kiichiro Hiranuma"s Cabinet. In this capacity he vigorously trumpeted the extension of aggression war， proposed to enhance military alliance with Germany and Italy， and plotted for the war with the Soviet Union. He issued an order in February in the name of the War Ministry， forbidding returning Japanese soldiers to talk about the atrocities they committed in China. In June he met Wang Jingwei twice， scheming to establish a puppet government headed by the latter.
On September 4， Itagaki was appointed Chief of Staff of the China Expeditionary Army. On July 7， 1941， he was promoted senior general， acting as Commander-in-Chief of the Chosen Army stationed in Korea. In 1943 he served as Supreme Military Counselor. He was appointed Commander-in-Chief of the 17th Area Army in Korea on February 1， 1945， and Commander-in-Chief of the 7th Area Army in Singapore on April 7， directing Japanese troops to fight the Allied forces in Indonesia and Malaya. On August 15， Japan declared unconditional surrender. In September Itagaki led the 7th Area Army to surrender to the British forces in Singapore.
Class-A war criminal to the gallows
After surrender， Itagaki tried in vain to buy over the Commander-in-Chief of British forces in Singapore with a huge sum of money. At the request of the Chinese military， the Allied forces arrested Itagaki in December， and escorted him from Singapore to Tokyo. Beginning May 1946 the International Military Tribunal for the Far East staged interrogations of 28 Class-A war criminal suspects including Itagaki that lasted more than two years. During the interrogation， Itagaki took all possible steps to quibble， but facing undeniable ironclad evidence， he had to plead guilty at last. The International Military Tribunal for the Far East decided him to be a Class-A war criminal on November 12， 1948 and condemned him to be hanged. He was sent to the gallows at Sugamo Prison on December 23.